Formation and Plate Tectonics

The Karakoram Mountains form the western side of the Himalaya Mountain Range. This range extends from the Pakistan-Afghanistan region into Tibet. Formation of this great mountain chain began when India drifted away from Gondwanaland (a land mass that consisted of all the southern continents of Pangea) and moved northwards colliding into Asia (as seen in The Break up of Pangea Diagram and Animation to the right), giving rise to the tallest mountains in the world (Windley 1988). This collision was caused by plate subduction. In the process of plate tectonics where two plates are converging, one plate will be pushed down by another plate as they come together (as seen in the two Subduction Diagrams to the right). During the formation of the Karakoram Mountain range, it is the Indian plate that was subducted by the Asia plate (Rex et al 1988). This under thrusting of the plates at continental convergence zones causes crustal thickening (crustal thickening is illustrated in the picture: Subduction Zone For Converging Plates), which is was ultimately formed the mountains (Rex et al 1988).  Although the Karakoram Plate is a subduction zone, scientists have found some strike-slip faults, some of which are still active (Kahn and Glenn 2006, and Rex et al 1988).  The biggest strike-slip fault in the region is called the Karakoram Fault and it extends about 800km in length. (Phillips et al 2004).

Mountains

            Within the Karakoram Mountain Range lies a sub range known as the Baltoro-Muztagh. This is home to the world's second largest mountain as it is over 8.6 km tall, which is just shy of Mount Everest (by roughly 200ft). It was originally named K2 as a reference to the 35 mountains peaks that are found with in the Karakoram, but later it was renamed Mount Godwin Austen after an explorer (image of K2 can be viewed on the left). Natives to the region, however, prefer to call the peak Chogo Ri or Qogir, both translating into "big mountain" (Encarta). In addition, the glaciers around it heavily impact this mountain. The arêtes and cirques are easily distinguishable and have been created by glacier movement (as seen in the picture to the left). The arêtes appear as steep jagged ridges that separate glacial valleys. These glacial valleys create the cirques, which take a semicircular shape at the top of where the glacier begins. Also found in this region is the Nanga Parbat peak which reaches a height of 8.1km.

Glaciers and Valleys

One process that still continues to create geomorphologic change is the formation of glaciers. These features have greatly impacted the landscape of the Karakoram Mountain to this day. Glacier movement has carved out landmasses of the mountains and left sediment deposits that have created valleys. There is a valley that surrounds every glacier, but they are not considered true "valleys" because they have interrupted depths due to mountain spurs that project out from the main valley areas. The moraine walls that separate most of these glaciers acts as a barrier to protect the lateroglacial valleys from glacial activities. The valleys can be as long as 20 km and as wide as several hundred meters (Iturrizaga 2001). The valleys that have been formed through glacial erosion are often broad and exhibit a "U" shape (see picture on right).  Iturrizaga also shows evidence that the largest lateroglacerial valleys are often formed by smaller glaciers. Glacieral deposits, commonly known as moraines, create the lateroglacerial valleys. These glacial sediment deposits can have distances of over tens of kilometers.  Aside from carving out valleys, the glaciers have also been responsible for the creation of temporary lakes that have become dammed by such glaciers, which has inevitably led to flooding. Some of the glaciers can be 2500m-5000m in thickness and run about 60km long (Iturrizaga 2001). These Mountains are home to the largest mountain glacier, the Baltoro Glacier. It takes part of its name from the ranges of mountains that it is situated between, which are called the Baltoro-Muztagh.  The Baltoro is so large that it can actually be seen from satellite images taken from space. In fact, the Baltoro is noted as the main trough glacier.  It acquires some of its mass to the glaciers around it that feed into it such as The Godwin Austen Glacier, the Gasherbrum Glaciers and the Abruzzi Glacier. All of the smaller glaciers that flow into the main trough are considered tributary glaciers.  

Glacier Expansion

An interesting occurrence that contrasts widespread evidence of glacier decline is that of glacial expansion in the central Karakoram region. Apparently this expansion only effects the glaciers that are sized over 7000m and are in elevations of 4500m in this region (Hewitt 2005). Although limited studies have been conducted to research this phenomenon, one major factor that has attributed to this is the change and effects of decreased temperatures. It has been found that in this specific region, there has been a drop in spring and summer temperature. This is highly contradictory to the weather conditions in east the Himalayas where there is definite glacier retreat, which is believed to be due to an increase in global warming (Fowler and Archer 2006).

The evidence for glacier expansion has primarily been found with 8 particular glaciers in the region that have displayed a renewed lateral moraine building. This moraine building exhibits thicker and more active ice, which has overridden moraines that were virtually ice free for the past 50 years (Hewitt 1998b). Although this thickening has been irregular in its occurrence, it has developed quickly where there had previously been thinning and recession according to studies conducted from 1985 to 1995 (Hewitt 1998a). Important ground observations that have clearly defined glacier expansion include, but are not limited to: A defined line that distinguishes active ice and passive margin; fresh ridges of lateral moraine next to the line of shear; and continuous sections of ice cliff that has risen past the glacier surface and surpassed overhanging glacier margins. In the past, features like this were rarely seen, but when they were observed, it was credited to Ice Age expansion. Now that they have become more commonplace, more research has found that climate and temperature change is the leading theory for such surges (Hewitt 2005). Table 1 to the list show a record of years that glacial surges have been reported as well as if there is a surge cycle associated with them. As the table reveals, the frequency of data is not sufficient to determine how often glacial surges occur. Ongoing research has not been established to provide such results.

Effects of Climate/Temperature

With a geographical location of roughly 36°N and 74°E, the region in which the Karakoram Mountains are located is extremely cold due to its high altitude. The global climate pattern of this region is noted as the Highland climate. Climates in this region are typically cool to cold with a lot of precipitation. This climate type is only present where there are mountains or high plateaus. There tends to be a lot of orographic precipitation, which makes the region very moist. (Strahler and Strahler, 2006). Climate stations have gathered substantial information to conclude that over the past 50 years, small declines in summer temperatures in particular have caused an increase in glacier mass due to increased precipitation. Surveys conducted from 1997 to 2002 showed that expansion has been found in 13 glaciers, sized from 10 to 20km, which have advanced and exhibited a thickening of 5 to 15m (Hewitt 2005). The animated diagram to the bottom left shows a simulated example of this type of glacial surge occurring from 1990 to 2000. The first glaciers to be identified for this phenomenon were the Baultar, Barpu, Hispar, and Biafo glaciers. Repeat photography and satellite imagery were able to assist in comparing the measurement of expansion from 1985 to 2001 (Hewitt et al 1989, Hewitt 1989), but much of the evidence has been accredited to ground observation.

            In the past, suggested theories of glacier expansion in the Karakoram region were thought to be a varying response to climate change, especially with regard to large influxes of monsoon snowfall (Kick 1989). But more recent research suggests that regional climate, seasonality, and recent climate change may all attribute to glacier expansion (Hewitt 2005). Climate studies have also shown 3 distinct weather systems that have had an impact on this region. There is a westerly circulation and cyclonic storms in the winter, an accumulation of heavy snow in the high-altitude also during the winter months, and monsoon advancement in the summer months. These monsoon storms produce cooler temperatures as well as additional snowfall (Kick 1989). Since increased precipitation creates cloudy skies, the net radiation that would normally be responsibly for 80 to 85% of glacier ablation creates another factor in why glacier expansion might be sustained. With an increase in winter precipitation and a decline in summer mean and minimum temperatures, there is substantial evidence that these factors in climate change correlate with the positive mass balance in glaciers (Fowler and Archer 2006).

            Since glacier mass balance is determined by the accumulation of snow on top of the glacier and the ice ablation on the bottom, research has found that the glaciers that have gained the most mass have been nourished by avalanched snow in addition to increased precipitation. Also, some glaciers have steep high rock walls or heavy moraine, which act to reduce ablation by trapping snow (Hewitt 2005).

Decreased Watershed and Its Effects

            A problem that has been created by the sudden glacier expansion is the impact it has on those glaciers in the high latitudes that previously had the highest watersheds.  Reduced flows have been reported for rivers dominated by glacier runoff draining the highest parts of the Central Karakoram. The watersheds from these glaciers directly affect the flow of the Indus and Yarkand rivers. Normally, melted seasonal snow, melted glaciers, melted permanent snow, and precipitation fuel watershed. Economic life in Pakistan largely depends on Agriculture, which in turn depends on irrigation (Archer 2003). Due to the decline of temperatures, decreased watershed has become a definite problem. Without sufficient watershed to these rivers, nearly 200 million people will be impacted, as there has already been evidence of a decline in river flow over the past two decades (Archer and Fowler 2004).

 

Landslides

            Another problem that has been identified in the Karakoram region with regard to river flow is the catastrophic effects that landslides have on the Indus River and its tributaries. Roughly 115 rock avalanches have been identified and 73 of these have formally dammed the Indus River, creating a naturally fragmented river system (Hewitt 1998). The geomorphic activity in this region is considered extreme due to snow avalanches, rock falls and slides, as well as debris flows and rivers that are prone to flooding (Hewitt 1998b). Rock avalanches that come from steep mountain walls form the landslides. When these landslides are deposited into the river, runout can occur, depending on the height by which the rocks fall as well as the mass of the rockslide. Glaciers also add to the equation by occasionally blocking tributaries in the higher parts of the Karakoram Range. This has created ice damming and outburst floods that have only complicated conditions in the region (Hewitt 1989). 

 

            Climatic and temperature drops continues to be a problem for the Karakoram Mountain region, as the change in these trends are causing geographical problems that cannot continue to be ignored. As stated before, there is an absence of ongoing research in this area due to its difficult location and the high costs associated with that. Because research has not been continuous, many disputes have developed that have formed discrepancies on the information concerning the actual amount of avalanches that have occurred as well as the theories surrounding why glacier expansion continues to be a phenomenon. Without ongoing research, it has and will continue to be very difficult to identify other factors that may attribute to glacier expansion as well as pinpoint other elements that could possibly explain the influences of glacial behavior.