The forces that work on the surface of the earth is known as __________________ or ____________________________.
Answers
Answer:
The forces that work on the surface of the earth is known as gravitational force or gravity.
Hope that this answer has helped you....
thank you and good bye...❤☺
Answer:
Despite our tendency to consider Earth as static, it is actually a dynamic and ever-changing planet. Wind, water, and ice erode and shape the land. Volcanic activity and earthquakes alter the landscape in a dramatic and often violent manner. And on a much longer timescale, the movement of earth’s plates slowly reconfigures oceans and continents.
Each one of these processes plays a role in the Arctic and Antarctica. We’ll discuss each in general and specifically in the polar regions.
EROSION
Wind, water, and ice are the three agents of erosion, or the carrying away of rock, sediment, and soil. Erosion is distinguished from weathering — the physical or chemical breakdown of the minerals in rock. However, weathering and erosion can happen simultaneously. Erosion is a natural process, though it is often increased by humans’ use of the land. Deforestation, overgrazing, construction, and road building often expose soil and sediments and lead to increased erosion. Excessive erosion leads to loss of soil, ecosystem damage, and a buildup of sediments in water sources. Building terraces and planting trees can help reduce erosion.
GLACIERS
In the Arctic and sub-Arctic, glacial erosion has shaped much of the landscape. Glaciers primarily erode through plucking and abrasion. Plucking occurs as a glacier flows over bedrock, softening and lifting blocks of rock that are brought into the ice. The intense pressure at the base of the glacier causes some of the ice to melt, forming a thin layer of subglacial water. This water flows into cracks in the bedrock. As the water refreezes, the ice acts as a lever loosening the rock by lifting it. The fractured rock is thus incorporated into the glacier’s load and is carried along as the glacier slowly moves.
Abrasion happens when the glacier’s ice and rock fragments act as sandpaper, crushing the rock into finely grained rock flour and smoothing the rock below. Meltwater streams of many glaciers are grayish in color due to high amounts of rock flour.
_meltwater_stream
Above-freezing temperatures created a meltwater stream on the Scott Glacier, Antarctica. Photo courtesy of BlueCanoe (Flickr).
Glacial erosion is evident through the U-shaped valleys and fjords that are located throughout the Arctic and sub-Arctic regions. Glacial moraines are formed as a glacier recedes, leaving behind large piles of rock, gravel, and even boulders. Moraines may form at the foot (terminal moraine) or sides (lateral moraine) of the glacier or in the middle of two merging glaciers (medial moraine).
u_shaped_valley
A U shaped Valley in Alaska.
moraine
Glacial moraine in Kyrgyzstan.
A fjord in Norway.
Photos courtesy (T to B) of Skylar Primm, Geir Halvorsen, and Martin Talbot (Flickr).
Coastal erosion has become a major issue in recent years in the Arctic, with Alaska’s North Slope losing as much as 30 meters (100 feet) per year! Climate change is thought to be the underlying cause. As the climate warms and sea ice melts, more of the sun’s energy is absorbed by ocean water. As this heat is transferred to the land, the permafrost (frozen soil) thaws, making the coast vulnerable to erosion from wave action and storms (which are more frequent due to warmer temperatures and open water). This video from the University of Colorado Boulder and the U.S. Geological Survey shows time-lapse images during one month of crumbling.
WIND
In Antarctica, katabatic winds play a large role in erosion. This type of wind occurs when high-density cold air builds up at high elevations (on the ice sheets, for example) and moves downhill under the force of gravity.
katabatic_winds schematic graphic
Image courtesy of Hannes Grobe, Alfred Wegner Institute for Polar and Marine Research (Wikimedia).
Katabatic winds in Antarctica and Greenland are intensely cold and fast, often reaching hurricane speed. You can hear these fierce winds in this YouTube video
The winds in Antarctica carry small grains of sand that scour and erode the exposed rocks, resulting in unusual shapes and formations. These oddly shaped, eroded rocks are called ventrifacts.
Ventrifacts are wind-eroded rocks found in the McMurdo Dry Valleys. They range from finger-sized to larger than houses. Photo courtesy of Kristan Hutchison, National Science Foundation.
PLATE TECTONICS
The theory of plate tectonics describes the motions of earth’s lithosphere, or outermost layer of hard, solid rock, over geologic time. Plate tectonics provides scientists with a great deal of information about the polar region’s past.
tectonic_plates
Tectonic plates. Image courtesy of Wikimedia.
Earth’s lithosphere is broken into seven major and many minor tectonic plates. These plates move in relation to each other, slowly changing the location of earth’s continents and oceans.