Tectonics, Earthquakes, Volcanoes
Chapter 13 4CE (Chapter 12 3CE)
“God is so wise and so mighty. Who has ever challenged him successfully?
Without warning, he moves the mountains, overturning them in his anger.
He shakes the earth from its place, and its foundations tremble.”
Job 9:4-6 (NLT)
**There is a video version of this lecture here: https://youtu.be/1U7k-dpTn-w
**The exam is based on the content in these notes, so please print them off to study from.
I. Crustal Movements
The Earth’s surface is changing. A variety of processes continually reshape the surface of the Earth.
A. Constructive and Destructive Processes
Some of these processes are constructive … the relief (landforms) normally becomes higher/rougher as a result. Mountains are raised up (like volcanoes), blocks of rock rise higher (like along faults). Chapter 13 looks at some of these constructive, Earth-building processes.
Some of these processes are destructive … the relief (landforms) tends to become lower/smoother as a result (for example, weathering, landslides, and erosion wear down mountains into hills). These destructive processes will be considered in Chapter 14 (weathering, mass movement, erosion).
These Earth-shaping processes are driven by energy that comes from two possible sources:
- endogenetic energy originates within the earth – for example, the energy from the earth’s interior appears to fuel the movement of crustal plates, volcanoes, earthquakes, etc. Endogenetic energy tends to result in constructive Earth-building processes.
- exogenetic energy originates outside the earth. The most important source of exogenetic energy is the sun. The sun’s energy is responsible for daily/annual cycles of heating and cooling. Exogenetic energy is responsible for weather and weathering, a destructive earth changing process. Exogenetic energy tends to result in destructive Earth-building processes
B. Orders of Relief
The landform formations on the earth’s surface are typically classified by orders of relief.
- First order of relief landforms are the biggest, global structures – continents and ocean basins. Thus North America, as a whole, is considered a first order landform. The Pacific basin is a first order landform.
- Second order of relief landforms are large features within a first order landform (a continent or ocean basin). Thus the Rocky Mountains or the Great Plains (prairies) are second order landforms in North America. The mid-ocean ridge in the Pacific or Atlantic Ocean basin is a second order landform.
- Third order of relief landforms are specific landform features such as individual mountains, river, or valleys. Thus Mt. Robson, the highest peak in the Canadian Rockies, is a third order landform. The Petitcodiac River in New Brunswick is a third order landform. The Fraser River Delta is a third order landform.
(Don’t worry about “hypsometry,” p. 385 (top of page; 4CE) or (p. 348, 3CE))
All continents have a foundation or backbone of solid igneous rock to which other rock formations are attached. This nucleus/foundation/backbone of a continent is referred to as a craton. A craton is defined as a part of the Earth’s crust that has attained stability, and has been little deformed for a prolonged period. Where the craton is exposed at the surface it is often called a continental shield. The craton/continental shield is typically very hard rock, like granite or basalt. Because these shields appear to be very old rock, they are often heavily weathered and glaciated. The Canadian Shield is a fine example of a craton (see Figure 13.4, “Continental Shields,” p. 387 / (12.4, p. 349 (3CE)).
Often large platforms of sedimentary rock “grow” over time, attached to these shields. These are formed from as minerals and rocks that are weathered from the shield are deposited along the edges of the shields. These platforms are solidly connected to the shields and reflect the shield (the source of their sediment) in terms of their mineral composition. The Great Plains of North America are an example. The plains are composed of consolidated sediment (sedimentary rock) and unconsolidated sediment (sand, silt, clay) that was weathered and eroded from the Canadian Shield. This sediment, eroded off the Shield, accumulates on the margin as the Prairies.
Other parts of the crust appear to move within the crustal plates. The big plates discussed in the theory of plate tectonics (Chapter 12) appear to be less solid than originally thought. Each big plate seems to be made up of many smaller pieces – including the craton, its platforms, plus many smaller pieces, called terranes. Generally, these pieces act together, functionally, as one large unit (a big plate).
However movement can occur between the various pieces of a plate (terranes) as well. North America, for instance, consists of a craton (the Canadian Shield), a platform (the Great Plains/Prairies) and many terranes (particularly along the western edge – the various mountain ranges that make up British Columbia). These terranes are distinct geologic regions (different in terms of mineral structures from the craton or the platform) – attached to the west coast.
The Rocky Mountains, mostly limestone (which is not found either in the Canadian Shield or on the Prairies), are an example of a terrane, attached to the Great Plains platform and the Canadian Shield craton. See Figure 13.6 /12.6, “North American Terranes,” p. 389 (4CE), p. 351 (3CE). Thus North America is a very complex geologic unit, composed of:
- a craton, the Canadian Shield
- a platform, the Prairies
- a series of terranes, the Rocky Mountains and other western mountain ranges
II. Crustal Deformation Processes
The rock material on the earth’s surface – the lithosphere – moves (tectonic activity) on top of the asthenopshere (the plasticy layer below the lithosphere). This can happen when terranes move within a big plate. Or it can happen as entire big plates move. As this movement happens, rock is subjected to stress. Forces push and pull the rock, causing a variety of effects …
A. Strain, Stress and Faults
Strain is how rocks react to stress. Some rocks are more “ductile” – they have a certain amount of flexibility and will bend or stretch in response to stress. Other rocks are more brittle – they will fracture or break in response to stress. Study Figure 13.7 / 12.7, “Three kinds of stress, strain …” p. 390 (4CE), p. 354 (3CE).
There are three types of stress:
Tension (side-to-side stretching or pulling apart)
When tension, side-to-side stretching or pulling apart occurs, ductile rocks will stretch, resulting in a thinner crust and a slight depression.
When tension, side-to-side stretching or pulling apart occurs, brittle rocks will break, creating a fault (a fault is a break or fracture in rock along which the rock moves). In this case, when the two blocks of rock on either side of the fault are spreading apart, it is called a normal fault. One side stays in place (the footwall side), the other typically drops (the hanging wall side). Study Figure 13.11 / 12.11, “Types of Faults,” p. 393 (4CE), p. 357 (3CE).
Sometimes a whole series of normal faults occur resulting in a series of blocks which stand as ridges, and blocks which have slipped down as valleys. This is referred to as horst (ridges) and graben (valley) topography. See Figure 13.13 / 12.13, “Faulted landscapes.” (4CE p. 396; 3CE p.360)
Shear (side-to-side twisting/tearing)
When Shear (side-to-side twisting/tearing) occurs, ductile rocks may bend horizontally (see Figure 13.7 / 12.7, “Three kinds of stress, strain …” p. 390 (4CE), p. 354 (3CE))
When Shear (side-to-side twisting/tearing) occurs, brittle rocks will break laterally and slide along side each other as a strike-slip or transform fault (the terms are interchangeable) (See Figure 13.11 / 12.11, “Types of Faults,” p. 393 (4CE), p. 357 (3CE)). The San Andreas Fault (an excellent website) is this kind of a fault.
Compression (side-to-side shortening or pushing together)
When Compression (side-to-side shortening or pushing together) occurs, ductile rocks will fold or bend in response to the stress. The result will be a series of upfolds and downfolds, like the interior of a piece of corrugated cardboard. (See Figures 13.7, 13.8 and 13.10 / 12.7-12.9, “Folded Landscapes,” pp. 390-392 (pp. 354-5, 3CE)).
a. Upfolds are called anticlines (shaped like the letter “A”). They typically form mountains of ridges. Typically oil and gas deposits accumulate in porous or permeable anticlines (oil and gas are lighter than water and tend to “rise” in anticlines). Thus petroleum geologists often choose to concentrate their exploration efforts in anticlines with porous rock. When you get a job as a geologist for a major oil company, remember this “anticlinal theory of petroleum accumulation.” You will be very successful!
b. Downfolds are called synclines (“Sin leads you down …”). They typically form valleys. See Figure 13.8 / 12.8, p. 391 (4CE), p. 355 (3CE). Note that oil and gas do not normally occur in synclines! Don’t waste your time or the company’s money looking there!
The Rocky Mountains contain many dramatic examples of folded rock.
When Compression (side-to-side shortening or pushing together) occurs, brittle rocks will break and slip, with one block sliding over top of the other to form a reverse or thrust fault (both terms interchangeable). See Figures 13.7, 13.8, and 13.11 / 12.7, 12.8, and 12.11. The hanging wall side rises over top of the footwall side.
A bit more on faults. Faults are breaks or cracks within rock, along which the rock can move.
Because faults represent breaks in rock and slippages of rock, earthquakes are very often associated with faulting.
Faulting has benefits however. Valuable minerals, buried deep below the surface, may be brought within reach of the surface along fault scarps, the cliff or slope formed when the fault moves:
Terms used to describe faults are:
- Dip – the angle between the cliff or scarp and the horizontal
- Strike – the compass direction along the fault plane
- Fault plane – the fracture line
- Scarp – the exposed cliff
Know the differences between
- normal fault: created by the stress of tension (pulling apart). One block of rock “falls” as the crust pulls apart. Remember a series of normal faults results in horsts (hills) and grabens (valleys) – See Figure 13.13 / 12.13, “Faulted landscapes,” p. 396 (3CE, p. 360). Head-Smashed-In Buffalo Jump, in southern Alberta, is a classic example.
reverse (thrust) fault: created by the stress of compression (pushing together). One block of rock is pushed over top of another. Do not worry about the differenced between reverse and thrust faults. Thrust faults are simply more dramatic examples of reverse faults. Mount Rundle, Banff, Alberta, was created by compression forces pushing rock layers over top of one another.
- strike-slip fault or transform fault: created by the stress of shearing (twisting). One block of rock moves sideways beside another. There are no scarps/cliffs in this type of fault, things shift laterally. The San Andreas Fault is a strike-slip fault (Figure 13.12 / 12.12).
The theory that mountains are “built” through crustal movements associated with plate tectonics – like faults – is called orogenesis.
Consider the different effects that different types of collisions would have on the Earth’s surface …
Oceanic plate-continental plate collision (Pacific coast of North America)
This would result in folded mountains, reverse faults, and much volcanic and earthquake activity. See “Three Types of Plate Convergence,” Page 399 (4CE), Figure a; (Figure 12.15a, p.361 (3CE)).
2. Ocean plate-ocean plate collisions (off Japan and Indonesia)
This would result in deep ocean trenches, earthquake and volcanic activity. See Page 399 (4CE), Figure b; (Figure 12.15b, p.361 (3CE)).
This would result in large-scale folded/faulted mountains. See Page 399 (4CE), Figure c.; (Figure 12.15c, p.361 (3CE)).
Read, but do not worry about studying in depth “The Western Cordillera,” “The Innuitian Mountains”, “The Appalachian Mountains” and “World Structural Regions”.
An earthquake is simply a motion of the ground surface (ranging from a faint tremor to a wild motion capable of causing substantial rock displacement and destruction of buildings).
A great reference page is the National Earthquake Information Center (U.S. Geological Survey), check out their “About earthquakes” page.
Also very good is the EarthquakesCanada website.
Many earthquakes occur every day, but are so slight they are only detectable by instruments (seismographs). See the links to the Canadian and U.S. government sites for updates on today’s quakes. There is also global information available.
Several areas in the world experience several moderate earthquakes each year (e.g. Aleutians, Japan, Central America, Indonesia)
A. Measuring Earthquakes
Earthquakes generate energy in the form of shock waves that move away from the focus (the exact point the quake occurred, often deep beneath the surface, also called the hypocentre), like ripples on a pond. They diminish in strength with distance. (Note: the epicentre is the point on the earth’s surface directly above the focus). Know this! The focus/hypocentre is the exact point the earthquake occurs. The epicentre is the point on the surface directly above the focus!
The quantity of energy released is the magnitude.
Magnitude is most commonly measured by the Richter Scale, developed in 1935 by Charles F. Richter, using a seismometer (also called a seismograph). It is a logarithmic scale (each whole number represents a 10X increase in wave amplitude). Thus the wave amplitude in a 6.0 earthquake is 10X that of a 5.0 quake.
In energy terms, each whole number represents a 31.5X increase in energy released.
Thus a 6.0 quake has 31.5X the energy of a 5.0
and 992X the energy of a 4.0.
- -3.0 – detectable by instruments
- 2.0 – just detectable by human senses
- 2.5-3.0 – felt nearby (about 100,000 globally per year)
- 4.0 – windows rattle
- 5.0 – windows break (same as Hiroshima atom bomb)
- 6.0 – destruction in limited area (100 globally per year)
- 6.0 – South Napa, California, 2014
- 6.2 – Central Italy, August 2016
- 6.3 – February 2011 and June 2011 Christchurch, NZ
- 6.5 – Los Angeles 1994 (Northridge)
- 6.9 – San Francisco (Loma Prieta) 1989, Kobe (Great Hanshin), Japan, 1995
- 6.9 – Morocco, 2023
- 7.0 – classified a major quake (14 globally per year) including Haiti 2010, Aegean Sea 2020
- 7.2 – Haiti 2021
- 7.3 – Iran-Iraq 2017
- 7.4 – Mexico 2020
- 7.5 – Sulawesi, Indonesia 2018
- 7.6 – Izmit, Turkey 1999
- 7.8 – Turkey-Syria 2023, New Zealand November 2016, Ecuador April 2016, Iran 2013
- 7.8 – Nepal April 25 2015 (aftershock May 12 2015, 7.3 magnitude)
- 8.0 – Samoa, 2009, Peru 2019
- 8.0 – Peru, August 15, 2007, Solomon Islands 2013
- 8.1 – New Zealand 2021, Chiapas, Mexico 2017
- 8,3 – 2015 Illapel earthquake, Chile
- 8.3 – San Francisco 1906, Sea of Okhotsk 2013
- 8.7 – Indonesia 2012, Sumatra, March 2005
- 9.0 – Sumatra, December 26, 2004 (major tsunami damage)
- 9.0 – Tohoku, Japan, March 11 2011 (earthquake and tsunami)
- 9.2 – Prince William Sound, Alaska 1964
- 9.5 – strongest ever recorded: Chile 1960,
An alternative measure of magnitude is the Moment Magnitude Scale.
The largest earthquakes by magnitude are:
|May 22, 1960||Valdivia, Chile||1960 Valdivia earthquake||9.5|
|March 27, 1964||Prince William Sound, Alaska, USA||1964 Alaska earthquake||9.2|
|December 26, 2004||Indian Ocean, Sumatra, Indonesia||2004 Indian Ocean earthquake||9.1–9.3|
|November 4, 1952||Kamchatka, Russia (then USSR)||1952 Kamchatka earthquakes||9.0|
|March 11, 2011||Pacific Ocean, Tōhoku region, Japan||2011 Tōhoku earthquake||9.0|
|September 16, 1615||Arica, Chile (then part of the Spanish Empire)||1615 Arica earthquake||8.8 (est.)|
|November 25, 1833||Sumatra, Indonesia||1833 Sumatra earthquake||8.8–9.2 (est.)|
|January 31, 1906||Ecuador – Colombia||1906 Ecuador-Colombia earthquake||8.8|
|February 27, 2010||Bio-Bio, Chile||2010 Chile earthquake||8.8|
|January 26, 1700||Pacific Ocean, USA and Canada||1700 Cascadia earthquake||8.7–9.2 (est.)|
|July 8, 1730||Valparaiso, Chile||1730 Valparaiso earthquake||8.7 (est.)|
|November 1, 1755||Atlantic Ocean, Lisbon, Portugal||1755 Lisbon earthquake||8.7 (est.)|
|February 4, 1965||Rat Islands, Alaska, USA||1965 Rat Islands earthquake||8.7|
|July 9, 869||Pacific Ocean, Tōhoku region, Japan||869 Sanriku earthquake||8.6-9.0 (est.)|
|September 20, 1498||Pacific Ocean, Nankai Trough, Japan||1498 Meiō Nankaidō earthquake||8.6 (est.)|
|October 28, 1707||Pacific Ocean, Shikoku region, Japan||1707 Hōei earthquake||8.6 (est.)|
|August 15, 1950||Assam, India – Tibet, China||1950 Assam – Tibet earthquake||8.6|
|March 9, 1957||Andreanof Islands, Alaska, USA||1957 Andreanof Islands earthquake||8.6|
|April 1, 1946||Aleutian Islands, Alaska, USA||1946 Aleutian Islands earthquake||8.6|
|March 28, 2005||Sumatra, Indonesia||2005 Sumatra earthquake||8.6|
|April 11, 2012||Indian Ocean, Sumatra, Indonesia||2012 Aceh earthquake||8.6|
|December 16, 1575||Valdivia, Chile (then part of the Spanish Empire)||1575 Valdivia earthquake||8.5 (est.)|
|November 24, 1604||Arica, Chile (then part of the Spanish Empire)||1604 Arica earthquake||8.5 (est.)|
|May 13, 1647||Santiago, Chile (then part of the Spanish Empire)||1647 Santiago earthquake||8.5 (est.)|
|October 20, 1687||Lima, Peru (Viceroyalty of Peru)||1687 Peru earthquake||8.5 (est.)|
|May 24, 1751||Concepción, Chile (Kingdom of Chile)||1751 Concepción earthquake||8.5 (est.)|
|November 19, 1822||Valparaíso, Chile||1822 Valparaíso earthquake||8.5 (est.)|
|February 20, 1835||Concepción, Chile||1835 Concepción earthquake||8.5 (est.)|
|August 13, 1868||Arica, Chile (then Peru)||1868 Arica earthquake||8.5–9.0 (est.)|
|May 9, 1877||Iquique, Chile (then Peru)||1877 Iquique earthquake||8.5-9.0 (est.)|
|November 10, 1922||Atacama Region, Chile||1922 Vallenar earthquake||8.5|
|February 3, 1923||Kamchatka, Russia (USSR)||1923 Kamchatka earthquakes||8.5|
|February 1, 1938||Banda Sea, Indonesia (Dutch East Indies)||1938 Banda Sea earthquake||8.5|
|October 13, 1963||Kuril Islands, Russia (USSR)||1963 Kuril Islands earthquake||8.5|
|September 12, 2007||Sumatra, Indonesia||2007 Sumatra earthquakes||8.5|
Another scale often used is the Modified Mercalli Intensity Scale, it measures not only magnitude, but also the human/engineering effects of an earthquake. Intensity ratings are expressed as Roman numerals between I at the low end and XII at the high end.
The Intensity Scale differs from the Richter Magnitude Scale in that the effects of any one earthquake vary greatly from place to place, so there may be many Intensity values (e.g.: IV, VII) measured from one earthquake. Each earthquake, on the other hand, should have just one Magnitude, although the several methods of estimating it will yield slightly different values (e.g.: 6.1, 6.3). Ratings of earthquake effects are based on the following relatively subjective scale of descriptions:
I. People do not feel any Earth movement.
II. A few people might notice movement if they are at rest and/or on the upper floors of tall buildings.
III. Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring.
IV. Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rock.
V. Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of open containers.
VI. Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage.
VII. People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings.
VIII. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water levels in wells might change.
IX. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage.
X. Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. Water is thrown on the banks of canals, rivers, lakes. The ground cracks in large areas. Railroad tracks are bent slightly.
XI. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent.
XII. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move.
Rating the Intensity of an earthquake’s effects does not require any instrumental measurements. Thus seismologists can use newspaper accounts, diaries, and other historical records to make intensity ratings of past earthquakes, for which there are no instrumental recordings. Such research helps promote our understanding of the earthquake history of a region, and estimate future hazards.
The Mercalli Scale is helpful because the earthquakes of greatest magnitude (according to Richter) are not necessarily the most lethal to people. In contrast, some earthquakes of lesser magnitude can have tremendous destructive capability. Here are the most devastating earthquakes on record, note that their magnitude was not always that high!
Most Destructive Known Earthquakes on Record in the World
Earthquakes with 100,000 or More Deaths
Listed in order of greatest number of deaths
- January 23, 1556, China, Shansi, ~8, 830,000 dead
- January 12, 2010, Haiti, 7.0, 316,000 (According to official estimates, 316,000 people killed, 300,000 injured, 1.3 million displaced, 97,294 houses destroyed and 188,383 damaged in the Port-au-Prince area and in much of southern Haiti. Other estimates suggest substantially lower numbers of casualties, perhaps as low as fewer than 100,000)
- December 26, 2004, Sumatra, 9.0, 283,106 (Deaths from earthquake and tsunami)
- July 27, 1976, China, Tangshan, 7.5, 255,000 (official) (estimates as high as 650,000)
- August 9, 1138, Allepo, Syria, 230,000
- May 22, 1927, China, near Xining, 7.9, 200,000
- December 16, 1920, China, Gansu, 7.8, 200,000
- December 22, 856+, Persia (Iran), Damghan, 200,000
- March 23, 893+, Persia (Iran), Ardabil, 150,000
- September 1, 1923, Japan, Kanto (Kwanto), 7.9, 143,000 (Great Tokyo Fire)
- October 5, 1948, USSR (Turkmenistan), 7.3, 110,000
- December 28, 1908, Italy, Messina, 7.2, 100,000
NOTE: the Japan earthquake (2011) had 15,756 deaths. The Nepal earthquakes (2015) had combined death tolls of approximately 9300. The Haiti (2021) earthquake had 2200-3000 deaths.
Since 1900, earthquakes with more than 1000 deaths continue to be of strong to moderate magnitude. More critical in the death count are building codes and other factors than just sheer magnitude.
B. Components of Earthquakes
- foreshocks – sometimes preliminary movement along a fault plane is detectable as small shocks
- principal or main shock – the “real” earthquake – when major movement occurs, the largest shocks occur over a period of seconds or minutes
- aftershocks – as the plates “settle” smaller shocks may occur hours or days after the principal shock
e.g. Mexico 1985 – an 8.1 Richter quake hit, located 350 km from Mexico City. The principal shock lasted 3 minutes; one aftershock was 7.6. Because Mexico City sits on silt, clay, sand and gravel in an old lake basin, the shaking caused the ground to settle: 7,000 buildings collapsed, 9,000 were killed, 30,000 injured and 95,000 left homeless.
e.g. Nepal 2015 – the April 25 main shock of 7.8 magnitude, followed by a major 7.1 magnitude aftershock on May 12. Over 9000 died in the first earthquake; over 200 in the aftershock.
4. tsunamis (sometimes misnamed “tidal waves” – they have NOTHING to do with tides!) occur when the plate movement causes water to rush into a depression and bounce back. They have nothing to do with tides! They have everything to do with earthquakes! The USGS has great illustration of how tsunamis develop and cause destruction.
e.g Tonga, January 14 2022. Tsunamis were observed throughout Oceania and Asia, western South America (2 m) and western North America (29 cm on Vancouver Island).
e.g. Sunda Strait, Indonesia, December 22, 2018. Hundreds were killed following a tsunami linked to an eruption and collapse of of Anak Krakatau volcano.
e.g. Tohoku, Japan, March 11, 2011 — waves of up to 40.5 metres in Miyako, Iwate, Tōhoku. In some cases traveling up to 10 km inland. In addition to loss of life and destruction of infrastructure, the tsunami caused a number of nuclear accidents, primarily level 7 meltdowns at three reactors in the Fukushima I Nuclear Power Plant complex, and the associated evacuation zones affecting hundreds of thousands of residents.
e.g. Sumatra, December 26, 2004 – The Sumatra tsunami was the worst (in terms of loss of life) tsunami in history. Among the issues were the number of people living in adjacent low lying coastal areas, lack of proper warning systems, and the speed with which the waves moved. This is the fourth largest earthquake in the world since 1900 and is the largest since the 1964 Prince William Sound, Alaska earthquake. In total, more than 283,100 people were killed, 14,100 are still listed as missing and 1,126,900 were displaced by the earthquake and subsequent tsunami in 10 countries in South Asia and East Africa.
e.g. Alaska 1964 – at 9.2 on the Richter Scale, this has been the most powerful North American earthquake. When the waves hit Hawaii they were moving at 640 km/h with crests 80 km apart. At Hilo (NE Hawaii), the waves were 14-30 m high, deposited 4 1/2 m of silt in the harbour, fish were thrown into palm trees and 125 people were killed (110 from the tsunami; 15 from the earthquake).
e.g. the only confirmed fatalities in a Canadian earthquake happened in a 7.2 quake, November 18, 1929 off Newfoundland (actually Newfoundland was not officially part of Canada, yet … but anyway …). 27-29 people in southern Newfoundland died in a tsunami caused by a large underwater landslide on the Grand Banks. The tsunami arrived in three waves, each up to seven metres high, that struck the coast at 105 km/h about three hours after the earthquake occurred. The tsunami destroyed many south coastal communities on the Burin Peninsula, killing 27-29 people and leaving 10,000 more homeless. All means of communication were cut off by the destruction, and relief efforts were further hampered by a blizzard that struck the day after. It took more than three days before the SS Meigle arrived with doctors, nurses, blankets, and food.
Canada has now developed more information on our potential tsunami risk and preparedness, too.
C. Earthquakes as hazards
Earthquakes really pose little direct danger to a person. People can’t be shaken to death by an earthquake. Some movies show scenes with the ground suddenly opening up and people falling into fiery pits, but this just doesn’t happen in real life.
- The first main earthquake hazard (danger) is the side-effects of ground shaking. Buildings can be damaged by the shaking itself or by the ground beneath them settling to a different level than it was before the earthquake (subsidence). Buildings can even sink into the ground if soil liquefaction occurs. Liquefaction is the mixing of sand or soil and groundwater (water underground) during the shaking of a moderate or strong earthquake. When the water and soil are mixed, the ground becomes very soft and acts similar to quicksand. If liquefaction occurs under a building, it may start to lean, tip over, or sink several feet. The ground firms up again after the earthquake has past and the water has settled back down to its usual place deeper in the ground. Liquefaction is a hazard in areas that have groundwater near the surface and sandy soil. Buildings can also be damaged by strong surface waves making the ground heave and lurch. Any buildings in the path of these surface waves can lean or tip over from all the movement. The ground shaking may also cause landslides, mudslides, and avalanches on steeper hills or mountains, all of which can damage buildings and hurt people.
- The second main earthquake hazard is ground displacement (ground movement) along a fault. If a structure (a building, road, etc.) is built across a fault, the ground displacement during an earthquake could seriously damage or rip apart that structure.
- The third main hazard is flooding. An earthquake can rupture (break) dams or levees along a river. The water from the river or the reservoir would then flood the area, damaging buildings and maybe sweeping away or drowning people.
- Tsunamis and seiches can also cause a great deal of damage. A tsunami is what most people call a tidal wave, but it has nothing to do with the tides on the ocean. It is a huge wave caused by an earthquake under the ocean. Tsunamis can be tens of feet high when they hit the shore and can do enormous damage to the coastline. Seiches are like small tsunamis. They occur on lakes that are shaken by the earthquake and are usually only a few feet high, but they can still flood or knock down houses, and tip over trees.
- Another earthquake hazard is fire. These fires can be started by broken gas lines and power lines, or tipped over wood or coal stoves. They can be a serious problem, especially if the water lines that feed the fire hydrants are broken, too. For example, after the Great San Francisco Earthquake in 1906, the city burned for three days. Most of the city was destroyed and 250,000 people were left homeless.
- Most of the hazards to people come from man-made structures themselves and the shaking they receive from the earthquake. The real dangers to people are being crushed in a collapsing building, drowning in a flood caused by a broken dam or levee, getting buried under a landslide, or being burned in a fire.
A list of all Canadian earthquakes is here. The strongest was an 8.7-9.2 magnitude quake off the west coast in 1700. In more recent decades, a 1949 Queen Charlotte Isands earthquake measured 8.1. The deadliest earthquake was the Newfoundland Grand Banks Earthquake 1929, with 27-29 deaths.
D. Earthquake Prediction and Engineering
To date no reliable predictive methods have been developed. See Earthquake prediction – Wikipedia, the free encyclopedia
Earthquake engineering is a growing field, as well. See also Earthquake engineering – Wikipedia, the free encyclopedia
The Transamerica Pyramid in San Francisco is one creative attempt to build a more earthquake-proof building. Check out the Earthquake Engineering Research Center (@ U California, Berkeley)
IV. Tectonics and Volcanism
(See Figure 13.22 (p. 411)/ 12.27 (3CE p. 376))
The Earth’s interior (endogenetic) energy appears to be the driving energy behind plate motion and volcanic activity. Volcanic activity typically occurs:
- at plate boundaries and appears to be associated with plate movement.
- or at isolated hot spots just below the surface, within plates (e.g. Hawaii).
** For details of current volcanic activity and up-to-the-minute websites, see: USGS Pages
2022 eruptions: Tonga,
- 2019 eruptions: Mount Sinabung; Indonesia, Stromboli, Italy; Whakaari / White Island New Zealand
** For information on Canadian volcanoes, check out the Canadian Volcanics page and Canada Volcanism on Wikipedia.
A great report on some of the world’s deadliest eruptions is here: BBC – Earth – The world’s most deadly volcanoes
For a great introduction to volcanoes, visit the U.S. Geological Survey’s Volcano pages.
- Old Faithful, the most faithful geyser in the world, erupts every 1.5 hours (give or take 10-15 minutes):
- check out the live “Old Faithful Cam”
The Smithsonian has a great Global Volcanism Program, with a database of volcanoes going back 10,000 years. Their new “Eruptions, Earthquakes, & Emissions” web application (or “E3”) is a great time-lapse animation of volcanic eruptions and earthquakes since 1960. It also shows volcanic gas emissions (sulfur dioxide, SO2) since 1978 — the first year satellites were available to provide global monitoring of SO2.
One of the most interesting people I’ve met is Dr. Bob White, a volcanologist – and Christian – at Cambridge University (academic website including details on reearach and publications). He has given several talks and written a number of articles (and books on Christian responses to natural disasters (speaking as an expert!), including:
- Natural-Disasters.pdf (Christians in Science pamphlet)
- “Are natural disasters acts of God?” A lecture given by Professor Bob White Audio
- White, Robert and Abbott, Roger (2020) What Good is God? Crises, Faith, and Resilience, Lion Hudson: Oxford.
- White, Robert and Moo, Jonathan (2013) Hope in an Age of Despair: The Gospel and the Future of Life on Earth, Inter-VarsityPress: Leicester.
- White, Robert (editor) (2009) Creation in Crisis: Christian Perspectives on Sustainability, SPCK: London.
- White, Robert and Spencer, Nick (2007). Christianity, Climate Change and Sustainable Living, SPCK: London.
- White, Robert (2005). “Truth in the geological sciences,” in Can We Be Sure About Anything? Science, Faith and Postmodernism (ed. Denis Alexander), Inter-Varsity Press: Leicester.
A. Types of volcanic activity
Effusive eruptions are generally less violent volcanic eruptions. These typically happen where plates are spreading apart. Here magma wells up to fill the cracks between the spreading plates, forming mid-oceanic ridges and volcanic islands.
Effusive eruptions are also often associated with sea floor spreading or isolated mantle plumes – hot spots – where mafic magma rises to the surface through weaknesses in the crust (e,g. Hawaii).
This magma is usually rich in mafic (dark in colour, heavy in weight) minerals and is very liquid. This allows much of the trapped gases to escape gently, resulting in relatively non-explosive eruptions. These mafic magmas have low viscosity (they are quite liquid), contain little trapped gas, cause quieter eruptions resulting in vast plateaus of lava or gently-sloped volcanoes.
These massive, gently sloping volcanic domes gently-sloped volcanoes are called shield volcanoes, because their profile resembles the bowed shape of ancient Greek shields. Because the magma is very liquid, they tend to have smooth, gentle slopes; they are often more than twice as wide as they are high. often shield volcanoes are found in island chains, caused wither by sea floor spreading, or as the crust moves over a mantle plume (e.g. Hawaiian Islands).
- for example, Mauna Loa, Hawaii rises 3900 metres above sea level, 9000 metres from its base: at sea level its is 16 – 80 km (16,000 – 18,000 m) in diameter; its base, at the sea floor is 190 km (190,000 m) wide. (Figure 13.27, p. 414 / 12.31, p. 378 (3CE))
- Mauna Kea, Hawaii, is 10,200 metres from base to top, higher than Mt. Everest is above sea level (8848 metres) — of course much of Mauna Kea is below sea level, only 4210 metres is above sea level.
- Kilauea, Hawaii, is one of the most active volcanoes in the world; it has been continuously erupting since 1983!.
- Mount Nyiragongo and Nyamuragira, Democratic Republic of the Congo (eruptions 2010, 2011-12, 2002, 1977) are shield volcanoes
- Galapagos Islands are an archipelago of shield volcanoes
- Iceland also has several small shield volcanoes
- Canadian example, Mount Edziza volcanic complex in northwestern BC is a vast, 1000 square kilometre shield volcano
Flood basalts are massive plateaus formed by very liquid mafic magmas “flooding,” or flowing over large areas. The magmas is extruded by extensive networks of fissures. For example, the Columbia Plateau (eastern Washington, Oregon, southern Idaho) covers several thousand square kilometres and measures up to 1 1/2 km deep.
Explosive Eruptions (sometimes called Plinian eruptions)
Explosive eruptions are much more violent than effusive eruptions. These typically occur where plates converge and one plate is subducted under another. The existing crustal rock, being forced downward, is melted. As it melts, it rises to the surface through cracks and weaknesses in the plates, erupting as a volcano.
The crustal rock that is subducted, melted, and then erupted, is often rich in silica (SiO2). This molten rock, rich in silica (felsic minerals – light in colour and weight) are relatively solid and very explosive when they are rise to the surface in a volcano. Felsic (silica-rich) magmas are not very liquid (rather, composed of solid rocks), contain much trapped gas, and cause explosive eruptions and dramatic mountains (volcanoes) made up of blocks, cinders, and ash. These are sometimes referred to as plinian eruptions.
There are several types of volcanoes created by explosive eruptions:
a. Cinder Cone
Cinder cones are relatively small piles of ash/debris from a violent volcanic eruption, usually a few hundred metres high. They are completely made up of ash and solid cinder blocks, normally created in a single eruption. For example, Paricutin, Mexico, was literally born overnight in a farmer’s corn field; within a few weeks it “cooled off” at an elevation of 450 metres.
- The Mount Edziza complex in NW BC includes over 30 cinder cones, formed after the original shield volcano.
- Parícutin, Mexico, is the most famous cinder cone; it emerged from a farmer’s field in 1943.
b. Composite Volcanos (Strato volcanos)
Composite volcanoes are the most common volcanoes formed by explosive eruptions. These are tall, steep-sided cones, usually sloping steeply to the summit where the crater is located. The main body of the volcano is formed of alternating layers of ash and lava, created by a series of several eruptions.
When they erupt, they also usually extrude a cloud of incandescent gases and very fine ash called a nuée ardente (literally, a ”glowing cloud”). This cloud of intensely hot gas is heavier than the air and flows down the slope, searing everything in its path.
Examples of composite cones include:
- Mt. St. Helens (see Figure 13.32, p. 417) which erupted May 18, 1980, blew off 4 cubic kilometres of material, lowered its summit by 400 metres, flattened every tree in a 400 square kilometre area, sent dust and ash around the world (10 cm was deposited in eastern Washington). The force of the explosion measured 5.0 on the Richter scale and was heard over 320 kilometres away. Mudflows caused by melting snow traveled over 130 km/h and clogged the Colombia River with silt. There are many excellent websites about Mt. St. Helens.
- Other volcanoes in the U.S. Pacific Northwest including Mt. Baker (visible from Vancouver, BC) and Mt. Ranier (near Seattle, WA) formed as a result of subduction along the Cascadia subduction zone where ocean plates are being subducted below the North American Plate. This string of volcanoes extends from southern B.C. through Washington, Oregon, and into Northern Caolidornia.
- Canadian examples include Coquihalla Mountain, Mt. Garibaldi, the Black Tusk, and Mt. Meager in southwestern BC, all part of the same Cascadian subduction zone as the U.S. examples, above
- Mayon, Phlippines (2013), the “perfect cone.”
- Mt. Pelée, Martinique (1902); the real “killer” was the nuée ardente which destroyed the city of St. Pierre and killed all but 2 of its 30,000 residents.
- Mount Vesuvius, which destroyed Pompeii and Herculaneum in 79 AD is a composite volcano
- Other composite volcanoes include Mt. Fuji (Japan), Mount Nyiragongo (Congo), and Mt. Kilimanjaro (Tanzania).
- In 2011, Grímsvötn, Iceland, erupted, disrupting air travel between North America and Europe for several weeks.
When an extremely violent explosive eruption literally blows a mountain apart leaving a huge depression in the centre, a caldera (Spanish for “kettle”) is formed. Often this becomes a lake, sometimes with another volcanic cone developing in the centre. These massive eruptions are sometimes referred by a new term, supervolcano (a popular term, not normally used by scientists yet, as it is not clearly defined).
For example, when Krakatoa, Indonesia erupted (1883), 75 cubic kilometres of rock disappeared into the atmosphere, leaving a caldera 6 km across. The resultant tidal waves killed 36,000 in Sumatra and Java.
When Katmai (Novarupta), Alaska erupted (1912), the explosion was heard in Juneau, 1200 km away; at Kodiak (160 km away), 25 cm of ash fell on the city. Severe earthquakes rocked the area for a week before Katmai exploded with cataclysmic force. Enormous quantities of hot, glowing pumice and ash were ejected from Katmai and nearby fissures. This material flowed over the terrain, destroying all life in its path. Trees up slope were snapped off and carbonized by the blasts of hot wind and gas. For several days ash, pumice, and gas were ejected and a haze darkened the sky over most of the Northern Hemisphere. When it was over, more than 40 square miles of lush green land lay buried beneath volcanic deposits as much as 700 feet deep. At nearby Kodiak, for two days a person could not see a lantern held at arm’s length. Acid rain caused clothes to disintegrate on clotheslines in distant Vancouver, Canada. The eruption was ten times more forceful than the 1980 eruption of Mount St. Helens.
Crater Lake, Oregon, was formed 7700 years before the present, when Mt. Mazama exploded, losing 1200 m in height, creating a caldera 8 km in diameter. A small cinder cone has subsequently developed from a small, more recent eruption. Oregon’s Crater Lake is just one of several such “crater lakes” around the world.
Yellowstone National Park, Wyoming, is largely located in a huge caldera (actually 3 overlapping calderas), 55 X 72 km across. The most recent eruption (many many centuries ago!) blew away 1000 cubic kilometres of rock and ash (more than 2500 times greater than Mt. St. Helen’s eruption in 1980). The magmatic heat powering those eruptions still powers the park’s famous geysers, hot springs, fumaroles, and mud pots. Over 50% of all known geysers in the world are located within the Yellowstone Crater. Here is an interesting piece: BBC News – Yellowstone supervolcano ‘even more colossal’.
Eyjafjallajökull, Iceland, is an active cone in a 3-4 kilometre caldera in a composite volcano. A 2010 eruption interrupted air traffic between North America and Europe for several days.
Canada has several calderas in BC, Ontario, Quebec, and New Brunswick:
- Silverthrone Caldera, BC
- Mount Edziza, BC
- Bennett Lake Volcanic Complex, BC/Yukon
- Mount Pleasant Caldera, NB
- Sturgeon Lake Caldera, ON
- Mount Skukum Volcanic Complex, Yukon
- Blake River Megacaldera Complex, PQ
d. Volcanic Necks or Volcanic Plugs
Given enough time, the softer layers of ash and lava in composite volcanoes and cinder cones may be eroded away, leaving the solidified core of the volcano (neck), standing as an isolated, jagged peak.
Devil’s Tower, Wyoming, is probably the best known.
A list of volcanic necks/plugs in Canada is found here: Volcanic plugs of British Columbia
B. Active, Dormant and Extinct Volcanoes
Volcanoes can be active for a few months of for several million years, perhaps having quieter times and more rambunctious times. Many of Earth’s volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of activity. Given the long lifespan of such volcanoes, they are very active. By our life spans, however, they are not. There are no hard and fast rules to determine whether a volcano is active, dormant, or extinct as it depends on what timespan we are considering. And some, like Moount St. Helens, can surprise us.
Scientists usually consider a volcano active if it is currently erupting or showing signs of unrest, such as unusual earthquake activity or significant new gas emissions. Many scientists also consider a volcano active if it has erupted in historic time (that is, time during which people have kept records (since 1000 BC or so).
Dormant volcanoes are those that have not erupted for thousands of years, but are likely to erupt again in the future. Most of the composite volcanoes in B.C., Washington, Oregon, California, (and Yellowstone National Park) are in this category.
Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Some volcanoes, for instance those on the Hawaiian Island chain that seem to be past the “hot spot,” or the volcanic plugs in Scotland (Bass Rock and Edinburgh Castle Rock) seem to be no longer geologically active.
C. Importance of Volcanoes:
Volcanoes are important features in the Earth-atmosphere system …
As natural hazard
a. An explosive eruption blasts solid and molten rock fragments (tephra) and volcanic gases into the air with tremendous force. The largest rock fragments (bombs) usually fall back to the ground within 3.5 km of the vent. Small fragments (less than about 1 mm. across) of volcanic glass, minerals, and rock (ash) rise high into the air, forming a huge, billowing eruption column. Eruption columns can grow rapidly and reach more than 20 km above a volcano in less than 30 minutes, forming an eruption cloud. The volcanic ash in the cloud can pose a serious hazard to aviation. During the past 15 years, about 80 commercial jets have been damaged by inadvertently flying into ash clouds, and several have nearly crashed because of engine failure.
Large eruption clouds can extend hundreds of miles downwind, resulting in ash fall over enormous areas; the wind carries the smallest ash particles the farthest. Ash from the May 18, 1980, eruption of Mount St. Helens, Washington, fell over an area of 40,000 km2 in the Western United States. Heavy ash fall can collapse buildings, and even minor ash fall can damage crops, electronics, and machinery.
The 2010 eruptions of Eyjafjallajökull caused major disruptions to air travel in Europe.
b. Volcanic Gases are also emitted during eruptions. Even when a volcano is not erupting, cracks in the ground allow gases to reach the surface. More than ninety percent of all gas emitted by volcanoes is water vapor (steam), most of which is heated ground water (underground water from rain fall and streams). Other common volcanic gases are carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, and fluorine.
Cataclysmic eruptions, such as the June 15, 1991, eruption of Mount Pinatubo (Philippines), inject huge amounts of sulfur dioxide gas into the stratosphere, where it combines with water to form an aerosol (mist) of sulfuric acid. By reflecting solar radiation, such aerosols can lower the Earth’s average surface temperature for extended periods of time by several degrees. These sulfuric acid aerosols also contribute to the destruction of the ozone layer by altering chlorine and nitrogen compounds in the upper atmosphere.
The only know fatalities associated with volcanism in Canada involved an eruption of Tseax Cone, a cinder cone, north of Terrace, BC. Between 1668 and 1714, a major lava flow eruption dammed two rivers and destroyed two villages. Approximately 2,000 people died from the volcanic gases and poisonous smoke, making it Canada’s worst known geophysical disaster.
c. Molten rock that pours onto the Earth’s surface forms lava flows. The mineral balance (mafic/felsic) affects its characteristics:
- Mafic lava, associated with less-explosive eruptions, flood basalts and shield volcanoes, can form fast-moving (15 to 50 km/h) streams or can spread out in broad thin sheets several kilometres wide. Since 1983, Kilauea, on the Island of Hawaii, has erupted basalt lava flows that have destroyed more than 200 houses and severed the nearby coastal highway. Mafic lava is often classified as:
- In contrast, flows of higher-silica felsic lava (composite volcanoes, cinder cones) tend to be thick and sluggish, traveling only short distances from a vent. Felsic lavas often squeeze out of a vent to form irregular mounds called lava domes. Between 1980 and 1986, a lava dome at Mount St. Helens grew to about 350 m high and 1200 m across.
d. Pyroclastic Flows are high-speed avalanches of hot ash, rock fragments, and gas that can move down the sides of a volcano during explosive eruptions or when the steep side of a growing lava dome collapses. These pyroclastic flows can be as hot as 1000°C and move at speeds of 150 to 250 km/h. Such flows tend to follow valleys and are capable of knocking down and burning everything in their paths.
Mount St. Helens generated a series of explosions that formed a huge pyroclastic surge. This so-called “lateral blast” destroyed an area of 400 square kms. Trees 2 m in diameter were mowed down like blades of grass as far as 25 km from the volcano.
The towns of Pompeii and Herculaneum, Italy, were engulfed by pyroclastic flows from Mount Vesuvius in 79 AD.
e. Volcanic Landslides: A landslide or debris avalanche is a rapid downhill movement of rocky material, snow, and (or) ice. Volcano landslides range in size from small movements of loose debris on the surface of a volcano to massive collapses of the entire summit or sides of a volcano. Steep volcanoes are susceptible to landslides because they are built up partly of layers of loose volcanic rock fragments. Some rocks on volcanoes have also been altered to soft, slippery clay minerals by circulating hot, acidic ground water. Landslides on volcano slopes are triggered when eruptions, heavy rainfall, or large earthquakes cause these materials to break free and move downhill.
At least five large landslides have swept down the slopes of Mount Rainier, Washington, during the past 6,000 years. The largest volcano landslide in historical time occurred at the start of the May 18, 1980, Mount St. Helens eruption.
f. Lahars: Mudflows or debris flows composed mostly of volcanic materials on the flanks of a volcano are called lahars. These flows of mud, rock, and water can rush down valleys and stream channels at speeds of 30 to 60 km/h and can travel more than 80 km. Some lahars contain so much rock debris (60 to 90% by weight) that they look like fast-moving rivers of wet concrete. Close to their source, these flows are powerful enough to rip up and carry trees, houses, and huge boulders miles downstream. Farther downstream they entomb everything in their path in mud.
Historically, lahars have been one of the deadliest volcano hazards. They can occur both during an eruption and when a volcano is quiet. The water that creates lahars can come from melting snow and ice (especially water from a glacier melted by a pyroclastic flow or surge), intense rainfall, or the breakout of a summit crater lake. Large lahars are a potential hazard to many communities downstream from glacier-clad volcanoes, such as Mount Rainier.
As Natural Resource
Volcanoes are not ALL bad news! They can also be beneficial – if we keep our distance!
a. Rich Soils. Volcanic ash and weathered basalt produce some of the most fertile soil in the world, which produce bumper crops of coffee, sugar cane, rice and corn in the tropics, and the healthiest forests in temperate regions. The land around volcanoes is very valuable as an agricultural resource.
b. Tuff is a relatively soft sedimentary rock formed from volcanic ash. Being soft and easy to work with, it has been used for construction from Roman times to the present day. Most of the well-known monolithic human figure statues (mo’ai) on Easter Island were also carved from tuff.
c. Ecotourism. Volcanoes possess a scenic beauty that can generate a lucrative tourist and recreation industry. This can inject millions of dollars, annually, into local businesses. Yellowstone National Park — whose features are almost all volcanic — is the most visited natural place in the United States!
d. Geothermal Energy. Mantle Plumes and other intrusions of magma close to the surface are responsible for bringing heat ffrom the Earth’s interior close to the surface. This is responsible for hot springs, geysers, and other subsurface water heating.
Geysers, hot springs, fumaroles, and mud pots are generally found in regions where surface water percolates downward through the rocks below the Earth’s surface to high-temperature regions surrounding a magma reservoir, either active or recently solidified but still hot. There the water is heated, becomes less dense, and rises back to the surface along fissures and cracks. Sometimes these features are called “dying volcanoes” because they seem to represent the last stage of volcanic activity as the magma, at depth, cools and hardens.
- Geysers provide spectacular displays of underground energy suddenly unleashed, but their mechanisms are not completely understood. Large amounts of hot water are presumed to fill underground cavities. The water, upon further heating, is violently ejected when a portion of it suddenly flashes into steam. This cycle can be repeated with remarkable regularity, as for example, at Old Faithful Geyser in Yellowstone National Park, which erupts on an average of about once every 65 minutes. Most geysers are much less regular or predictable.
- Hot springs occur in many thermal areas where the surface of the Earth intersects the water table. The temperature and rate of discharge of hot springs depend on factors such as the rate at which water circulates through the system of underground channelways, the amount of heat supplied at depth, and the extent of dilution of the heated water by cool ground water near the surface. Hydrogen sulfide (H2S), one of the typical gases associated with hot springs readily oxidizes to sulfuric acid and native sulfur. This accounts for the peculiar smell and brightly colored rocks in many thermal areas.
- Fumaroles are simply gas vents — hot springs in which all the water is evaporated before it reaches the surface.
- Mud pots are thick, thick hot springs — clay minerals are mixed with the hot water to cause boiling mud!
Geothermal heating has been tapped as an energy source since ancient times. Hot springs were used for bathing since antiquity. More recently, large-scale commercial power stations have exploited its value for electricity generation, space heating, spas, and industrial processes.. Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly, but is limited, on a large scale, to tectonically active areas near plate boundaries (like Iceland). On a small scale, developing geothermal heat pump technology has allowed geothermal energy to be used in individual buildings in less active areas.
Worth reflecting on …
A reflection on the eruption of the Iceland volcano Bardarbunga by Dr. Bob White, Professor of Geophysics at Cambridge University. He describes the wonder of this spectacle and how it relates to his own Christian faith: Notes from a Volcano – Science and Belief
Check out this video clip “Does science threaten belief in God: Fine Tuning”: http://www.youtube.com/watch?v=ncsuh_5l6Hw&list=PL99B2AA9CE8133639
Reflecting on the subject, “The need of science and Christianity for each other,” New Zealand author, Dick Tripp, concludes:
“If science and Christianity need each other, then how should we handle conflict? It will obviously help a lot if we recognise the truth of physicist Sir William Bragg’s famous saying:
Religion and science are opposed…but only in the same sense as that in which my thumb and forefinger are opposed – and between the two, one can grasp anything.
Both Christianity and science are seeking to understand the truth – what is really there. Truth does not conflict with itself. It is only our perceptions of what is really there that differ – and that is because none of us has the whole truth.
Harvard scientist J. H. Van Vleck, summarising the profound philosophical significance of Werner Heisenberg’s “uncertainty principle”, stated:
The least arguable conclusion is that man should remain humble in the face of nature, since there are inherent limitations to the precision with which he can observe.
We all need a good dose of humility, not least in our understanding of the Bible in those areas where Biblical scholars disagree. The philosopher Whitehead said, “A clash of doctrines is not a disaster – it is an opportunity.” He continued: “A mere logical contradiction cannot in itself point to more than the necessity of some readjustment, possibly of a very minor character on both sides.” And we need to respect the right of others to hold their opinions in those areas where we do disagree.
I will close this section with three quotes which aptly summarise the need of science and Christianity for each other. The first is by John Polkinghorne in an article in the Daily Telegraph. Polkinghorne is a theoretical physicist and a member of the Royal Society. He was a professor of mathematical physics before his ordination to the Anglican ministry in 1983. Today he is president of Queens’ College, Cambridge, and has been one of the leaders in what seems to be a growing contingent of British physicists who are engaging in meaningful theological discussion. He says: Men of religion can learn from science what the physical world is really like in its structure and long-evolving history. This constrains what religion can say where it speaks of that world as God’s creation. He is clearly a patient God who works through process and not by magic. Men of science can receive from religion a deeper understanding than could be obtained from science alone. The physical world’s deep mathematical intelligibility (signs of the Mind behind it) and finely tuned fruitfulness (expressive of divine purpose) are reflections of the fact that it is a creation.
The second quote is from the eminent philosopher Alfred North Whitehead. He observed:
When we consider what religion is for mankind, and what science is, it is no exaggeration to say that the future course of history depends upon the decision of this generation as to the relations between them.
The third quote, which I like most of all, comes from Gordon Cooper, American Astronaut, who named his spacecraft “Faith 7”. He said:
At an altitude of more than 150 miles over the Indian Ocean, I had faith and thanked God for the privilege of being on the space flight. Our launch team had faith in God, in the hardware we had developed and in each other. As we learn more about the universe we gain greater faith in the work of the Supreme Architect. Upon contemplating the complex workings of millions of planetary bodies – and the unknown immensity of the universe – we realise what a fantastic miracle it all is, including our little earth.”
For a really helpful discussion of how science and faith can come together, see Faith, science, and metaphors by Shiao Chong is the Christian Reformed Chaplain serving York University in Toronto, Canada.
Feel free to discuss these on the course discussion site (see the syllabus for details …)
To Review …
Check out the resources at www.masteringgeography.com
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Scripture quotations marked (NLT) are taken from the Holy Bible, New Living Translation, copyright © 1996. Used by permission of Tyndale House Publishers, Inc., Wheaton, Illinois 60189. All rights reserved.