Glacial landforms - Remote Sensing Application - Completely Remote Sensing, GPS, and GPS Tutorial
Glacial landforms Part-2

Another Antarctic glacier is Byrd, named after the famed explorer Admiral Richard Byrd, who explored both the North and South Polar regions:

The Byrd glacier, in the Antarctic.

This glacier is advancing at a moderate rate. But the current fastest-moving glacier is the Jacobshavn Glacier in Iceland. Here is a Landsat-7 image on which is superimposed lines for the glacier's toe or front in the years indicated.

The Jacobshavn Glacier, with red lines showing the advancing front for the years indicated.

However, evidence is growing that most of the world's glaciers have been receding (retreating) in the last 30 or so years, probably in response to either a natural interglacial warming or man-induced global warming, or perhaps both. The new land being exposed is very evident in the Columbia Glacier in Alaska along its coast, as photoed from the air:

Aerial view of the retreating Columbia Glacier, in Alaska.

Glaciers in the Himalayas show this continuing condition of retreat. The mountain glaciers in Bhutan shown here are shrinking and developing new lakes at their termini - solid indications of diminishing glacial active in that region.

Receding mountain glaciers in the Bhutan part of the Himalayas

Glaciers in the Kharakoram Range in the western Himalayas show similar slow recession:

Glaciers in the western Himalayas.

Glaciers also come off great ice sheets such as the one covering most of Greenland. This view (ASTER) shows the sheet's edge and flowing glacial ice emptying into Baffin Bay on the northwest corner of this subcontinent (across from Ellesmere Island and north of the Thule Air Base).

Glacial ice coming off the Greenland Ice Sheet near Baffin Bay; ASTER image.

Generally, when one thinks about where glaciers are likely to occur on Earth, the first response would be in the colder regions, such as the Arctic and Antarctic. But, as evident from several of the above examples of glaciers they can also occur in the higher altitudes of mountain ranges. It may seem surprising to learn that glacial ice can be found even in the tropics and temporal latitudes. This next image shows an ice field not far from the Equator. This is the Qualccaya Ice Cap in northern Peru.

The Qualccaya Ice Cap.

U-shaped valleys are commonplace in the Alps of Switzerland. This Landsat scene shows widened valleys in the alpine region of that country:

Glaciated valleys in the Alps.

The Alps have been extensively glaciated. Some spectacular scenery is the result. Probably the best known single glacial landmark in Switzerland is the famed Matterhorn (which the writer first viewed from nearby Zermatt). It results from the meeting of aretes produced by cirque coalescence.

Ground view of the Matterhorn.
The Matterhorn and other features in a satellite image.

This partial Landsat scene in the Trollaskagi region of northwest Iceland provide a post-ice view of an ice-sculpted mountainous area where glaciers, now gone, have left conspicuous troughs (wide valleys) with intervening ridges now sharply creased into aretes. Several large fjords are formed where seawater has encroached into larger glacially-scoured lowlands.

 U-shaped (cross-section) valleys in the glaciated Trollaskagi region of Iceland, in this partial Landsat image.

Fjords were treated briefly two pages back in the segment dealing with coastal landforms. But fjords are primarily expressions of glacial action in which the U-shaped valleys carved by now retreated or vanished glaciers that had reached the coastline are now drowned by marine waters. In the next sequence of images we will look at several more examples of fjords:

First, another look at Norwegian fjords:

A fjord in Norway.
Ground view of a Norwegian fjord; Photo Credit: Eric Bassman.

Similar fjords are found in Alaska.

Glacier Bay, Alaska.

In Patagonia (Chile) the Andes reach to the Pacific. A long line of fjords develop. Some of these occupy valleys that originally were developed along structural lineaments.

Fjords along the Chilean coast.
A closer view of a Chilean fjord.

Mountain glaciers once were common in the 48 U.S. states. Most have now melted but conspicuous glacial landforms remain. Here is a satellite view of glaciated valleys in Glacier National Park in northwestern Montana:

Glacial valleys in the Rocky Mountains of Montana.

The Uinta Mountains of Utah were also glaciated. In this view, aretes (thin ridges) and cirques (ice-sculpted amphitheaters developed at the highest points in individual glaciers) are evident:

Cirques and aretes in the Uinta Mountains.

Several advances and retreats occurred (at least four, perhaps more in North America). Today with that ice almost gone from North America, the land once covered has been notably modified by both erosional and depositional glacial landforms. Southern New England is a good example of a land surface affected both by erosional scouring and deposition:

The glaciated terrain in southern New England.

Deposits of moraine and till in places are several hundred meters thick. Depositional landforms are harder to make out in many space images but here are two examples, both from Canada.

The first shows glacial scouring, fluting, alignment of lakes, and morainal surfaces and till plains in the Northwest Territories.

Glaciated surface of the Northwest Territories, Canada, with fluting and till deposition dominant; Landsat MSS.

This second image is a Landsat subscene that shows megafluting (areas of scraping kilometers wide) in the Nunavat Territory of Arctic Canada.

Broad grooved (scraped) surface of the Canadian Shield in northern Canada.

This satellite image shows megafluting in more detail:

Satellite image showing megagrooves.

Another example of ice flow features are these fluted and ribbed moraines and crag-and-tail hills in the Ungava Bay district of northern Quebec. These are subtly expressed in the "grain" of this Landsat-1 image; the ice flowed in a southwestern direction:

Ice flow features and glacial lakes in the Ungava Bay  district.

Now we turn to drumlins again. As a reminder, here is a detailed look at drumlins within an aerial photo

Aerial photo of a field of drumlins; the thin tapered end of these low hills points in the direction of ice advance.

This next image is a Landsat MSS subscene that includes a field or swarm of drumlins, elongated low, cigar-like hills of glacial till that were molded into this shape during a moderate glacial advance. They appear after the ice melts and retreats. Note the direction of motion from the northeast.

Landsat subscene of northern Saskatchewan in which the glaciated surface is dominated by elongate drumlins trending southwest.

Seasat viewed a large drumlin swarm in northwest Ireland, as seen here. The term "drumlin" is Irish, being given long ago to these peculiar hills.

Seasat radar image of the topography of a part of northwest Ireland in which the landscape is dominated by drumlins.

Another satellite image shows drumlins in Clew Bay, Ireland.

Now, on to a final topic for this page: A survey of landforms associated with dominantly subfreezing high latitude terrains in the northern hemisphere. Large sections of Alaska, Canada, and Russia lie at latitudes where temperatures move above freezing for only part of a year. The ground remains frozen just beneath the surface all year round - this is referred to as permafrost. The term is sometimes interchanged with "periglacial" which has the more general connotation of "regions beyond moving ice bodies where freezing is prevalent most of a year" The ecology of such regions is distinctive, with the term "tundra" being restricted to the particular vegetation - lichens, small plants, limited numbers of trees - that make up this biome. The modern day distribution of permafrost is shown in this map:

Distribution of permafrost in the northern hemisphere.

Here are ground scenes typical of periglacial terrain:

Typical periglacial terrain.
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>Here are two satellite views of tundra terrain in Siberia:

Landsat image Siberian tundra.
Landsat image Siberian tundra.

One of the hallmarks of periglacial terrains is the common occurrence of numerous small lakes. Some, called kettle lakes, are water-filled depressions made by the melting of blocks of ice.

How a kettle lake is formed.
Kettle lakes in Alaska.

Also sometimes called thaw lakes, many kettle lakes are aligned in a directional orientation, such as seen here:

Aligned kettle lakes.

Lakes are common in the Siberian tundra:

Siberian lakes.

Another hallmark is called 'ice wedge polygons' or 'patterned ground'. It is fairly widespread and certainly distinctive. Look at three photos which display its characteristics.

Patterned ground.
Patterned ground
Patterned ground.

One would expect this feature to be well documented by aerial photos and satellite images. But, the writer spent almost two days looking for just one such illustration on the Internet. Result: one meagre possibility (but patterned ground images for Mars were located). Here it is (where and what unknown, as Internet hit was poorly documented).

Patterned ground in an aerial photo (?).

The last landform to be considered is called a "pingo". Here is an example:

Pingos in the Northwest Territory of Canada.

The mode of formation of pingos requires the action of water from beneath the permafrost layers. The process is summarized in this direct quotation from the Wikipedia site for that name:

"Hydrostatic-system pingos form as a result of hydrostatic pressure on water from permafrost, and commonly form in drained lakes or river channels. Permafrost rises to the drained body's former floor. Pore water is expelled in front of the rising permafrost, and the resulting pressure causes the frozen ground to rise and an ice core to form. The shape and size of a hydrostatic or closed system pingo is often similar to the body of water that it originated from. They can vary from symmetrical conical domes to asymmetric, elongate hills. Hydraulic-system pingos result from water flowing from an outside source, subpermafrost or intrapermafrost aquifers. Hydrostatic pressure initializes the formation of the ice core as water is pushed up and subsequently freezes. Open-system pingos have no limitations to the amount of water available unless the aquifers freeze."

Pingos and kettle lakes are present in this satellite image of permafrost terrain in Siberia.

Terrain including pingos and kettle lakes near the Ob River in Siberia.

This ends our tour of highlighted, thematic images from "Geomorphology from Space." You can see more, with detailed captions, on the Internet Site mentioned above or in the CD-ROM prepared by JPL. If you study the book, the Web Site, or the CD-ROM, please look at Chapter 11 that presents an effort by Dr. Robert S. Hayden to demonstrate the value of Landsat imagery in geomorphic mapping. Although he was not the first to produce this type of map solely from space imagery (C.F. Pain's 1985 map of an area in New South Wales, Australia is one early example), he has put together excellent examples of this capability.

Source: http://rst.gsfc.nasa.gov