Chapter 17a-b Glaciers and Glacial Landforms
Geosystems, 4CE, pp. 533-564 (Geosystems, 3CE, pp. 515-549)
Snow and ice are part of the Canadian experience! 77% of the Earth’s freshwater is frozen — mostly in Greenland and Antarctica. The rest is located on mountains and in valleys around the globe. Worldwide, all glaciers are retreating (melting) faster than ever before (one of the key objective indicators of global warming!). This has implications for local water supplies … and for global sea levels — all that water has to go somewhere! The objective data demonstrate that global ice packs are shrinking and sea levels are rising — that’s indisputable reality.
In this chapter we think about the processes involved in ice, particularly glaciers, as they form the landscape.
Some terms to know:
A Glacier is defined as a large accumulation of ice, on land or floating as an ice shelf attached to land.
A glacier forms when, on average, winter snowfall, exceeds summer snow ablation (removal of snow and ice by melting and sublimation [direct evaporation into the atmosphere]). In other words, a glacier can form when, over time, more snow arrives than leaves!
Glaciers are normally categorized as:
Continental Glaciers or Ice Sheets – in Arctic and Polar Regions, prevailing temperatures are low enough that snow and ice accumulates over vast areas. Entire continents, including both mountain ranges and lowlands, may be covered with ice several kilometres thick. Antarctica and Greenland are current examples. In both of these locations, the ice is more than 3000 metres thick. Technically these are larger than 50,000 square kilometres (you don’t need to remember this trivia!)
Ice Caps – are vast ice sheets that are currently limited to high summit areas, but (during cooler climatic conditions) may expand to become continental glaciers. Iceland and the Canadian Arctic islands are examples of landmasses with ice caps. See Figure 17.5; p.539 “Ice cap and ice field” (Figure 17.6; 3CE, p. 520). Technically these are smaller than 50,000 square kilometres (you don’t need to remember this trivia!)
Ice Fields – are large expanses of ice, smaller than ice caps. Mountain peaks and ridges protrude through the ice as nunataks (”islands” of rock surrounded by the sea of ice — not angry religious sisters!). The Columbia Ice Field, between Banff and Jasper, is a local example. See Figure 17.2; p. 535 (Figure 17.3; 3CE, p. 518).
Alpine Glaciers – in mountainous regions, at sufficiently high altitudes (even in tropical areas), air temperature is low enough and snowfall is sufficient to cause snow and ice accumulation as alpine glaciers. This is what we usually think of when we think of a glacier. These are common in most high alpine ranges such as the Rockies, the Alps, the Andes, and the Himalayas. See pages 542-3 “Glaciers as dynamic systems” (or Figure 17.7 “A retreating alpine glacier …” 3CE, p. 521)
I. Background – Ice Ages [4CE, pp. 553-558; 3CE, pp. 536-544]
Evidence suggests that periodically in the past climatic changes have been associated with occurrences of massive glaciation. Tillite (loose sediment churned up by glaciers [called till], converted into rock), fossils found in many strata of different ages, and erratics (rocks that appear to have been moved thousands of kilometres from where they ought to be), suggest repeated glaciation over much of North America and Europe.
- Till: loose, unsorted sediment deposited by glaciers
- Tillite: rock formed when till is compacted into solid form
- Erratics: rocks that geologically belong in a completely different location, apparently transported huge distances by continental glaciers. Two famous Canadian erratics are the Okotoks Erratic (claiming to be the largest is the world) and the Airdrie Erratic, both part of the Foothills Erratics Train. In this case, a whole series of rocks have been transported from near Jasper, 100’s of km southeast into south central Alberta, where they do not “fit” geologically.
There appear to have been several major “ice ages” in the past. During these ice ages, there are cooler and warmer periods — the ice periodically advances and partially retreats (interglaciation).
Some scientists currently contend we have been in an ice age for the past 2 1/2 to 3 million years, although we are currently in a period of interglaciation within our ice age (in other words, we are in a warmer cycle of an ice age). The glaciers appeared to reach their furthest advance possibly about 18,000 years ago, covering all of Canada and much of the U.S. (Figure 17.25 4CE, p. 556; Figure 17.28, 3CE, p. 539) “Extent of pleistocene glaciation”). Relatively rapid deglaciation began possibly about 15,000 years ago. The evidence for continental glaciation — such as erratics and other glacial erosion and deposits — is overwhelming. The causes of ice ages are a mystery (at least 54 explanations have been proposed). Possible causes are categorized as:
1. Terrestrial (change in conditions on Earth)
- Ice ages may be caused by a reduction of atmospheric CO2, which absorbs the suns heat and “insulates” the earth. A reduction would mean global cooling. Changes in global vegetation patterns or simply atmospheric changes could cause this.
- Ice ages may be related to periods of intense volcanism. Increased atmospheric dust would block solar energy, resulting in global cooling. Volcanic dust could also act as nuclei for moisture condensation, causing more precipitation (in cool climate, as ice and snow).
2. Astronomical (changes in space)
Ice ages may be related to variations in solar energy (A reduction of solar energy that caused even a slight drop in global temperatures would make a huge difference!)
- Ice ages may be caused by meteoric dust clouds (in space, between the sun and earth) blocking solar radiation.
- Ice ages may be related to changes in the distance between the Earth and Sun. The Earth’s orbit is not perfectly round but elliptical – currently it is closest to the sun during the Northern Hemisphere’s winter; if we were furthest during winter, temperatures could drop and ice could advance!
Among the effects of ice ages appear to have been:
- Lowered sea levels (about 100 m lower) as more water was frozen in ice. Vancouver Island would have been connected to mainland B.C. Britain would have been connected to mainland Europe. Siberia would have been connected to Alaska. Of course much of these regions would also have been covered by ice, even though they were above sea level!
- Vast areas would have been eroded and shaped by ice movement and deposition (see below).
The exploration of the role of human activity causing climate change has led to much concern and speculation about accelerated glacial melting (Then and now: Photographers document rapid melting of world’s glaciers) … and the consequences for the Earth including raised sea levels ...
As global temperatures rise (which they have been doing … take the other Geography course), the extent of ice sheets, ice caps, ice fields, and continental glaciers has been decreasing. All that water has to go somewhere! One of the consequences is raised sea levels. This has profound implications given that over 30% of the Earth’s population (think of lowland regions of China, India, Bangladesh, and the Gulf Coast – New Orleans) live only one or two meters above sea level, or even below sea level, protected by dikes/levees.
II. Glaciers as Systems
All glaciers (alpine, continental, or ice caps) are open systems. Their inputs, from outside, include snow, rock debris and solar energy. Outputs, things that leave, occur through melting, sublimation and sediment deposition.
Glaciers grow through the addition of:
- snowfall – the major source of glacial ice is from direct snowfall on the glacier’s surface, which is then compacted. Snow is also added by being blown off adjacent rocks (glaciers form in valleys, natural “drift” areas), and from avalanches.
- ice – ice may be added directly to glaciers as rime, formed when super-cooled water droplets freeze to a surface below 0°C (freezing rain, runoff freezing)
Glaciers “grow” like sedimentary rock. Layers are continuously added. The oldest ice is at the bottom; the youngest near the surface. Scientists use cross-sections of glacial ice to study pervious climates. They can determine which years were exceptionally cold and wet (thick layers of ice), and which years were much warmer or drier (thin layers or no layers of ice). The ice often contains frozen plant/animal remains which gives information about past climates and vegetation conditions.
The zone of accumulation is the part of a glacier where net accumulation takes place. In this region:
- accumulation exceeds ablation
- more snow and ice is added each year than is removed by melting or sublimation.
In alpine glaciers, this is the upper area. In continental glaciers it can happen all over. Firn refers to the dense, granular snow left in this zone after summer melting has occurred; it gradually compacts into ice. Firn is not the light fluffly snow that first falls. But the tough, granular snow that has made it through a summer of almost melting and refreezing.
The zone of accumulation is usually bright white (clean) snow … because it is relatively recent and has not been “stained” by lots of rockfalls, blowing dirt, and pollution.
Glacial ice forms as this firn (old snow) is compacted and recrystallized. The rate of ice formation varies with the rate of snowfall, melting, and the snow temperature.
e.g. Seward Glacier, Alaska – firn/ice boundary 13 m deep; firn becomes ice in 3-5 years.
e.g. Plateau Station, Antarctica (colder, drier): firn/ice boundary 160 m deep; takes 3500 years to become ice.
During summer much of the snow that falls onto the glacier, plus existing glacial ice, is lost by ablation (melting and sublimation.
The zone of ablation is that part of a glacier where net ablation takes place (ablation exceeds accumulation). In alpine glaciers it is normally the lower portion. In continental glaciers it can occur anywhere. The zone of ablation is usually greyish (dirty) snow and ice … because it is relatively old and has been “stained” by lots of rockfalls, blowing dirt, and pollution.
The processes of ablation include:
- sublimation – direct conversion of ice to water vapor
- Melting and runoff – occurs because of
- direct solar energy (heat)
- water (runoff from melting ice or rainfall), running over the surface, percolating through the ice, or running underneath the glacier.
- pressure melting – ice may melt at temperatures below 0° when the weight of the overlaying ice lowers the melting point of the ice (e.g., Byrd Station, Antarctica: melting occurs 2164 m deep at a temperature of -1.6°).
In many glaciers, the base is “relatively warm” (believe it or not) because of liquid water (above 0 degrees) percolating down from the surface, friction (ice moves up to 20 m per year), and geothermal heat (e.g. in Iceland, the ice caps are formed on top of active volcanoes). We tend to think of glaciers as colder deeper down. In fact, in thick glaciers, the base may be warmer than the surface! The base may be at or just above 0 degrees (because of water flowing, friction, and/or geothermal heat), while the surface is much colder! On a cold winter’s night, the surface of the Columbia Icefield may be -20ºC to -30ºC, while the base may by 0ºC!
A jokulhaup (“glacial burst”) refers to a sudden flood of water caused by subglacial volcanic activity rapidly melting glacial ice When volcanic activity suddenly melts the overlying glacier, bad things happen!
e.g. At Nevado del Ruiz (Columbia), subglacial volcanic activity melted a portion of the icefield on the mountain; the meltwater combined with volcanic mud killed 23,000.
e.g. At least two smaller jokulhaups have occurred on Cathedral Mountain (Yoho National Park, B.C.) in the past 125 years, causing snow and debris avalanches that have blocked the C.P. Railway and the Trans Canada Highway. Cathedral Mountain is not a volcano, but there is hot groundwater relatively close to the surface because of faulting, folding, and the porous limestone/sandstone formations (remember our discussion of hot springs in the Rockies).
- Calving – glaciers which end in a lake or ocean often lose large blocks of ice (icebergs) which break away. This process of breaking away is called calving. This is particularly common in areas where continental glaciers extend into the ocean, often as floating ice shelves (Antarctica, Alaska, Greenland, Arctic Ocean).
For a dramatic video, check this out: http://www.upworthy.com/they-took-a-camera-to-a-remote-area-in-greenland-and-what-they-recorded-is-simply-terrifying?g=3&c=ufb1
C. Glacial Balance
See pages 542-3 “Glaciers as dynamic systems” (or Figure 17.7 “A retreating alpine glacier and mass balance” 3CE, p. 521)
Glaciers have a balance point between the zone of accumulation and ablation, called the firn line. Above the firn line, accumulation exceeds ablation (and firn is found); below this line ablation exceeds accumulation (no firn).
On most glaciers it is relatively easy to spot the firn line. Above the firn line, the ice is normally quite clean and white. This is this year’s snow. It hasn’t melted. So it hasn’t gotten “old” and dirty yet (from windblown particles). Remember, above the firn line is the zone of accumulation, where more snow falls than melts in any given year.
Below the firn line, the ice is often “dirty-looking.” This is old ice. Remember, below the firn line is the zone of ablation, where more snow melts than falls. So, all the nice, clean, fresh this-year’s snow has long since melted. And what is left is much older firn/ice that has had time to collect windblown particles, moraine rocks (see below), etc.
So the firn line is the line between the nice clean new snow (in the zone of accumulation, higher up) and the dirty old ice (in the zone of ablation, lower down).
On any glacier the firn line may vary from year to year a little bit due to changes in climate (snowfall and temperature).
Long-term climatic changes will cause the glacier to have a trend of either advancing or retreating. If temperatures in a region are gradually getting cooler overall, glaciers will advance (the snout — the lowest point — will move further downhill); the glacier will get longer. If temperatures are gradually getting warmer, glaciers will retreat (the snout — the lowest point — will retreat further uphill); the glacier will get shorter. One of the evidences for global warming is that glaciers on all continents are retreating.
You will explore this in the lab as you look at the Athabasca Glacier over time. Visit it in the next decade or two … or it may not be around any more.
D. Glacial Ice Movement
Ice moves; that is an essential component of the glacial balance (otherwise the zone of accumulation would grow bigger; the zone of ablation would wither away, and a bizarre feature would result!) Instead, the ice slowly “flows” from the zone of accumulation to the zone of ablation, recharging the area of net loss. That’s why there is firn/ice in the zone of ablation, even though more melts in any given year than falls. The firn/ice flows from higher up, down to the zone of ablation.
Ice moves by three main processes:
See Figure 17.6 4CE, p. 540 (Figure 17.9 3CE, p. 523), “Glacial movement”
- Creep occurs as slow movement due to the pressure of overlaying ice and the force of gravity. The glacier is heavy! It’s resting on a slope. And glacial ice is a little bit flexible (like very cold putty). So the force of gravity, pulling on the great mass of ice, slowly pulls it downhill. Creep occurs more in summer when the ice is warmer; because the warmer ice is more easily deformed and tends to bend like plastic. Creep is most important at the base of the glacier where the effect of pressure, due to the weight of overlaying ice, is greatest.
- Basal Sliding; the base of the glacier is often lubricated by water (from runoff, rainfall, and friction) so the ice “slides” more easily under the influence of pressure or gravity. Some glaciers are frozen to their beds (called cold-based glaciers, see below); these don’t slide. Most cold-based glaciers are relatively small. These glaciers are too small to have enough weight to caused creep, and hence friction, and hence melting. Other glaciers rest on a layer of liquid water (warm-based glaciers, below); these can slide relatively well. Larger glaciers tend to be warm-based … paradoxically. Large, heavy glaciers are big and heavy enough to cause creep, which causes friction, which melts the ice at the base, which causes basal sliding. If you see a glacier with a river of water draining from underneath its snout, you likely have a warm-based glacier that is sliding (very, very slowly!) downhill.
- Fracture may happen when ice moves over an irregular bed, creating a series of deep fractures or crevasses (when the stresses on the ice exceed its cohesive strength). Ice is putty-like or plastic-y … a little bit. But it will also crack when flowing over major bumps. Crevasses indicate the bed is very uneven. Crevasses are a major glacial hazard. Fresh snows will often blow over top of them, either hiding them altogether or creating snow bridges. When you are happily walking across what appears to be solid ice, beware!
Rates of Ice Movement
The speed with which ice moves varies with the pressure (depth of ice), gravity (slope), temperature, and the amount of basal water.
Glaciers are often differentiated as either warm-based glaciers (deep enough to cause pressure melting at the base) and cold-based glaciers (too shallow for pressure melting, frozen to the bed). Paradoxically, large deep glaciers move more easily than small, shallow glaciers because they have a greater mass, which is more likely to cause creep, which causes friction, which causes melting, which causes water flow at the base!
During summer, large warm-based glaciers may move more than 4-5 m per day. During one period of volcanic activity in Iceland (1963-4), the Bruarjökull Glacier moved 5 km\h for 8 km; for ice, that’s hyper speed! Small cold-based glaciers may move less than a centimetre per day.
Within a glacier, the rate of movement is greatest at the surface, in the centre (like a water stream), where ice is carried along by underlying layers of ice and gravity, and where friction with the bed is least. The rate of movement is least on the edges and along the bed, where the ice may be frozen to the rock, or friction with the rock may slow it down.
Check out The Fastest glacier on Earth (moves 40 m per day) – awesome BBC video
III. Glacial Erosion
Glaciers can carry sediment in three different ways:
- on the surface – called supraglacial sediment
- within the ice – called englacial sediment
- at the base of the ice – called subglacial sediment
Glaciers vary in terms of how much sediment they carry in each location. They way sediment is carried will affect the glaciers appearance, how it erodes its bed, and depositional forms it may create.
1. Processes of Glacial Erosion
Some sediment comes from other gradational processes such as chemical or physical weathering or mass wasting. These processes may loosen bedrock and provide debris that a glacier can pick up. This material is already detached by the time it gets to the glacier. It often falls onto the surface from surrounding cliffs. This appears to have been the case with the Foothills Erratic Chain and the Okotoks/Airdrie Erratics. The amount and size of debris likely resulted from a landslide in the Rockies.
Abrasion occurs when ice and debris transported by the ice grinds against the bed, scraping and prying away fragments of rock. The amount of abrasion is related to the velocity of the glacier, its thickness, and the amount of sediment it is transporting.
Freeze – thaw processes are important where water on the base of warm-based glaciers penetrates cracks in the bedrock and refreezes. As the glacier moves, it can pull apart the rock to which it is frozen from the bed.
Some blocks of rock and debris may fall directly onto the glacier’s surface from surrounding cliffs.
Some materials may be carried onto the glacier by wind or water.
Debris at the base may be “picked up” as ice that has been pressure-melted refreezes around rocks and particles.
Debris may be “ploughed ahead” of the glacier by the snout and dragged along underneath the moving ice.
Subglacial material is often dragged along; this material is called a ground moraine. If a glacier is in retreat the ground moraine is left behind as mounds of rock, and loose debris called till. Till is simply the loose deposits left behind by a glacier – an unsorted mixture of rock, sand, silt, and clay.
Englacial material flows with the ice (unlike wind or water, in which the mass of transported material is related to velocity, ice can carry very large material as easily as small, light material). If a glacier is retreating, it is dropped and left behind, adding to the ground moraine as more till.
Supraglacial material is carried as moraines on the surface.
Moraines along the edges of the glacier, composed of debris that falls from, or is scraped away from the rock walls are called lateral moraines.
When two glaciers merge, two lateral moraines merge, forming a moraine in the middle of the glacier, called a medial moraine.
** See pages 542-3 (or Figure 17.7 “A retreating alpine glacier” (3CE, p. 521)). Find the lateral moraine and medial moraines! Understand how, why, and where they are formed.
If a glacier is retreating, these lateral or medial may be left behind as long ridges of debris.
Moraines at the snout (lowest end) of a glacier are called terminal moraines. If the glacier is retreating, several older terminal moraines may be evident further down the valley. These are referred to as recessional moraines.
Check out lateral and recessional moraines on the Athabasca Glacier.
- Small-Scale Effects
- striations are grooves or deep scratches in the bedrock, caused by rough rocks and particles caught in the glacier’s base gouging the rock. They line up with the direction of ice movement.
- chatter marks are lateral (right-angle) grooves in the bedrock caused by flakes or chips of the bedrock being pried away by the ice. These area at right angles to the direction of ice movement.
- polishing – fine clay and silt particles carried by glaciers over hard bedrock can create very smooth surfaces that look like they have been polished.
- potholes and stream channels may be cut by subglacial streams.
- Alpine Glacial Landforms
Study Figures 17.10 & 17.11 4CE, pp.545-6 “An alpine valley…” & “The geomorphic handiwork of alpine glaciers” (Figure 17.11 & 17.12, 3CE, p. 525-6 “Alpine glaciers occupy valleys” & “The geomorphic handiwork of alpine glaciers” ).
Alpine glaciers create highly eroded landscapes:
- deep, straight U-shaped Valleys are created as glaciers widen and deepen existing river valleys (stream valleys are typically V-shaped).
- Glaciers tend to cut away any ridges that protrude into the valley, producing truncated spurs.
- Between glacial valleys are steep sided, sharp-edged ridges called arêtes, and pointed peaks called horns. Alpine glaciers erode back into the cliff, creating knife-edged aretes and sharp horns.
- Side valleys feeding into a larger, deeper valley are referred to as hanging valleys. Because tributary glaciers in these side valleys tended to be smaller, they did not erode their bed as deeply as the larger, heavier main glacier. Thus, when all the glaciers melt, the main glacial U-shaped valley is cut much deeper than the side valleys. The side valleys appear to “hang” part way up the side of the main valley. Streams running our of these hanging valleys may form spectacular hanging waterfalls.
- Alpine glaciers tend to erode bowl-shaped basins called cirques. If the glacier melts a small lake often remains in the cirque, called a tarn. Some cirques contain a series of small, circular tarns arranged in steps down the valley, called paternoster lakes (“Pater noster” is Latin for “Our Father,” the first phrase of the prayer used with the Rosary – these lakes, arranged like beads on a chain, supposedly look like Rosary beads).
Most cirque glaciers have a permanent crevasse near the top called a bergschrund. The thin, uppermost stretch of the glacier remains frozen to the upper rock face. The thick, heavy, lower 95+% of the glacier flows downhill. In essence, the glacier pulls apart — the uppermost part frozen tight to the rock; the lower majority of the glacier flowing downhill. Rock falling from the cliffs above may be transported to the glacier base down this large crevasse. Mountain climbers are very aware of these crevasses. Cirque glaciers are often easier to climb than the surrounding rock, but the bergschrund can be a formidable obstacle.
When two cirques cut back towards each other far enough, a col, or semi-circular pass, or may be formed. (“col” is the French word for pass)
- when a U-shaped glacial valley is flooded by rising sea levels, a long, narrow, steep-sided bay called a fjord (or fiord) is formed.
Study these landforms! They make great exam material!
Continental Glacial Landforms
Continental glaciers tend to reduce topography over wide areas (lowering mountains to rounded hills, like the Appalachians, Atlantic Canada, and the Canadian Shield).
Continental glaciers cause widespread striations, polishing, etc.
- In areas of softer rock they carve out hollows, creating lakes when retreat occurs (northern Ontario and Quebec are dotted with tiny lakes, carved by glaciers out of the Canadian Shield).
- Roche moutonnées are rocky hills of resistant bedrock: typically they have a smooth, rounded stoss side (the side from which the glacier came), and an irregular, blocky, steep lee side caused by the ice plucking out large blocks. See Figure 17.9, 4CE, p.545 “Roche moutonnee” (Figure 17.18, 3CE, p. 530) “Glacial erosion streamlined rock”
C. Depositional Landforms
Continental glaciers deposit material in the ways:
- as glacial till, rock and debris deposited directly by the glacial ice (ranging from fine particles to huge boulders)
- as glaciofluvial (glacial river) deposits (till)
- as glaciolacustrine (glacial lake) deposits (till)
Glacial rivers and lakes are never clear, but often muddy or green/blue because the water contains many fine, suspended sediments and particles, many of which reflect specific wavelengths of light, creating dramatic colours. Many glacial lakes are dramatic blue or green colours, because the fine glacial sediment suspended in the water reflects light in these wavelengths.
Erratics are rocks that geologically belong in one region, that have been transported (often thousands of kilometres) to a location that is completely unrelated to their geologic structure (see above).
- Subglacial Landforms
Study Figure 17.16, 4CE, p. 548 (Figure 17.17; 3CE, p. 529) “Landforms associated with continental glaciation”
- flutes – small ridges of till (less than 1 metre high); these are the remnants of small subglacial stream beds. (A stream, flowing under the ice, deposits sediment on its bed. The stream level “rises.” The stream, however, is trapped side-to-side by ice. So the stream bed sediment piles up in the subglacial stream channel. When the glacier melts, this stream bed sediment remains as a sinuous mound)
eskers – long sinuous ridges of till (often several meters high) which may be 100’s of kilometres long and several metres high; these are the remnant river beds of subglacial rivers. Eskers are the same as flutes except are MUCH larger in scale. Flutes are small (less than 1 metre high), and tend to relatively short (a few tens or hundreds of meters long). Eskers are much larger (up to several metres high), and longer (hundreds of kilometres). Flutes are from subglacial creeks; eskers from subglacial rivers!
drumlins – large, streamlined hills (up to 200 m high and up to 5 km long), formed by subglacial floods piling sediments in glacial caverns. These are made of till, not solid rock. Often many drumlins are found in the same location. (Streams flowing under the ice tend to carve out hollows or caverns. Sediment can accumulate in these subglacial chambers. When the ice melts, these mounds of sediment remain).
- Landforms Along Glacial Margins
- lateral moraines – till along edges of glacier. Like alpine glaciers, continental glaciers accumulate sediment along their edges. Continental glacial lateral moraines are obviously much bigger than alpine glacial lateral moraines!
- terminal moraines – till mounded up at the snout. Like alpine glaciers, as a glacier retreats, several terminal moraines may form parallel ridges charting the retreat (referred to as recessional moraines). Again, the continental versions are much more extensive than alpine ones!
ice-cored moraines – as ice melts, a block of ice may be trapped in the middle of till. When this block of ice eventually melts, it may form a depression with a small lake in it, called a kettle lake. The ridges between kettle lakes are called kames. Kames also do occur at the snouts of alpine glaciers, but are much more common, and much larger, when associated with continental glaciers. Kettles/kames result in hummocky terrain, with a series of depressions (kettles) and gravelly hills (kames).
- An outwash plain is the area that is affected by runoff from the glacier. If the glacier is retreating, it is often made up of till left behind as a ground moraine. Because this is loosely consolidated, unstable material, and runoff varies tremendously seasonally, braided rivers are most common. Again, this is similar to the material at the snouts of alpine glaciers. But outwash plains are much larger and more extensive when associated with continental glaciers.
Worth reflecting on …
Ian Hutchinson is a professor of nuclear physics at MIT. Check out his biography:
Sir John Houghton, a fine Christian, is an expert on climate change: http://www.youtube.com/watch?v=nahiNo2IHV0&list=PLE6A9EBFA8C3C4046. Houghton was the co-chair of the Nobel Peace Prize winning Intergovernmental Panel on Climate Change’s (IPCC) scientific assessment working group. He was the lead editor of first three IPCC reports. He was professor in atmospheric physics at the University of Oxford, former Chief Executive at the UK’s Met Office (equivalent of Environment Canada).
Peter Harris, founder of the international Christian conservation organization, A Rocha (Portuguese for “the Rock”) writes:
Caring for Creation – the new frontier of mission
For many Christians who care about the world, the current environmental crisis seems not only to be out of reach, but more properly left to others of a more political turn of mind. Christian caring has traditionally focused exclusively on human need in all its many and desperate forms, but its environmental causes or context have rarely seemed to figure in the picture. However, we are living in remarkable times as the church worldwide is recovering its ecological conscience, and many opportunities to rediscover ways of making Jesus known as Lord by caring for his creation are opening up around this needy world. So it is long overdue for us to look again at some of the reasons for what has proved in the past to be tragic Christian indifference, but is now becoming a new frontier of Christian mission. We need to recognise that it is Christian leaders in the poorer world who are prompting us to see how the devastation of the environment is impacting church and society, and who are asking some of the following questions:
- If what surrounds us is God’s handiwork and not merely the human environment or human resources, as secular groups would have it, isn’t that some indication that we should look after it?
- What is the biblical basis for such a concern for creation?
- We now recognise that environmental causes more than any others are contributing to human suffering. They have led to more people becoming refugees in the last decade than warfare, and lie behind over half the world’s disease. So isn’t that sufficient reason for us to re-consider if we need to get involved?
Is creation care biblical?
The way the Bible frames the question, “What is Christian mission?” is to ask us who Jesus is, and what it means to follow him as Lord. Many passages serve as examples: the first chapters of Mark’s gospel are among the clearest presentations of many. Through a series of episodes, Mark introduces us to Jesus – Lord over sickness, religion, politics, the personal life. And then as he tells us of Jesus stilling the storm, he makes it clear that he is Lord over the weather, and by extension over all creation. This goes far beyond seeing the story as simply a reassurance of personal comfort in times when the weather gets rough and the boat of our personal life threatens to be overwhelmed. Equally, from the beginning of Genesis to the final promises of Revelation, the biblical story is one of God’s love reaching out to his whole creation, and supremely to people within it. Nothing else can explain the promise of the first covenant in Genesis 9:17: “This is the sign of the covenant I have established between me and all life on earth”, or the ringing hope of Romans 8:19-21: “The creation itself was subjected to futility… in hope that the creation itself will be set free from its slavery to corruption into the glorious freedom of the children of God”. The Bible understands that those who follow Jesus as Lord are led straight into relationship with him, and thereby to the restoration of all their relationships, personal, social and with the wider creation itself. We never find the biblical call to mission beginning with people, then simply trying to work out from there what the most pressing needs they face are. This agenda owes more to the humanism of the renaissance and enlightenment than a robust Christian world view that begins with the question, “Who is God, and how can we make him known in the world?” The logjam in evangelical thinking that has so sadly opposed social action to evangelistic endeavour, rather than understanding both as a consequence of the knowledge that Jesus is Lord, is only one of the consequences of this false point of departure. For people like ourselves, raised in a post-enlightenment culture that puts people and not God at the heart of our thinking, such a re-ordering doesn’t always come naturally but we cannot but admit that it is more biblical.
Does creation care matter?
It is unlikely at best, and incoherent at worst, to imagine that God is indifferent to the widespread destruction of what he has created. To think that we can claim on the one hand to love God, and then to be indifferent to his creation, or even worse to live destructively, is even more tragic. As has been well said, “It is impossible to say you love Rembrandt while you trash his paintings.” Set the wonderful promise of God’s redemption of creation against some of the current statistics – worldwide we risk losing fifty per cent of the meagre four per cent of plants we have already managed to describe in the wonderful treasure house of biodiversity which God has made. Some groups such as birds are less dramatically at risk – only twelve per cent will be lost in the next fifty years it seems – but then there are only just over nine thousand species to start with. What we are witnessing is casual, widespread, catastrophic destruction even while our awareness of the causes becomes ever more clear. We are in fact seeing the consequences of religious choices as human society on the western consumer model opts for personal comfort at the cost of the survival of the wider creation.
A distinctively Christian response
So much for the beginnings of a theology for creation care, but how can it work out in practice? How does the wonderful prospect of hope for creation take shape in particular places in our own times? For the last twenty years, A Rocha has been working to show how a distinctively Christian response can bring protection to endangered areas and species, and new hope to embattled human communities. Behind it all is a Christian witness that recognises the relevance of the gospel to everything God has made. Now working in fifteen countries including Portugal, Lebanon, Kenya, and the Czech Republic, teams are conducting scientific research, educational programs, and through living communities often based in field study centres, they are living out in practice what the gospel means to all comers. From the Alvor marshes of Portugal, to the Arabuko-Sokoke forest of the Kenya coast, or the Bekaa Valley marshes of Lebanon, and even on the post-industrial waste ground of the Minet site in Southall, England, where an A Rocha team has led the creation of a country park, there are grounds for hope. These habitats that would otherwise have faced severe threats may now continue to show something of the wonder of God’s care in creating remarkable and beautiful biodiversity, and the communities around them have the chance to know more of their Creator and Redeemer. For each one of us, where we live, there are opportunities to include our daily interactions with the created world in the dialogue of our discipleship.
Over the years understanding of the crisis overtaking the creation has been greater in the secular world of environmental NGOs of many different kinds than in the church. However, many of the secular groups now realise that questions of belief are fundamental to finding solutions, and several of them have begun to see how a Christian response can bring vital new insights to intractable problems in nature conservation. The Christian community worldwide has a remarkable opportunity to recognise the essential role of creation care in the task of mission, and to learn to live and work differently. As the crisis deepens, events will make this ever more urgent, and we must pray that our biblical convictions, and our relationship to Jesus the Creator and Lord, will lead us to act before it is too late.
(“A Rocha is a Christian nature conservation organisation, our name coming from the Portuguese for “the Rock,” as the first initiative was a field study centre in Portugal. A Rocha is now a family of projects working in Europe, the Middle East, Africa, North and South America, Asia and Australasia. A Rocha projects are frequently cross-cultural in character, and share a community emphasis, with a focus on science and research, practical conservation and environmental education.”)
How do you feel about Harris’ comments? Do you agree? Feel free to discuss this quote on the course discussion site (see the syllabus for details …)
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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