The formation of landscapes depend on the rock underneath the land- this is called the bedrock. Harder rock will be harder to breakdown. There are 2 forces in motion when it comes to determining landscapes. The first is erosion which removes rock from Earth's crust causing elevation to decrease. The second battling force is uplift which is when the crust goes upward causing an increase in elevation. The constant back and forth between erosion and uplift ultimately end in more of one than the other. Think of it like this, if you spend more money then you earn, you are in debt, but if you earn more than you spend, you are saving money. When more uplift than erosion occurs, mountains and plateaus form. When more erosion than uplift occurs, the resulting landscape is a plain or a lowland.
"Climate also plays a large role in the formation of landscapes/ Depending on location areas that are dry (arid) have very little vegetation present with large canyons. An area that is humid will get moderate to high amounts of precipitation. This leads to large amounts of vegetation and well-defined soil profiles. Humid areas are also known for their rounded hills. Bedrock effects how the landscape looks according to its resistance to its resistance to weathering and erosion. Stream drainage patterns are influenced by rock beneath them. There are 4 main types of stream drainage patterns. They are known as DART:
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Chemical weathering cave formation:
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Water travels down a stream the same way a car travels down a windy road. It has to slow down to take a sharp turn but can take the outside of the turn faster. When water moves quickly it has the ability to carry bigger sediments. Water travels faster on the outside bend compared to the inside bend. Erosion occurs when water travels quickly and deposition happens when water slows down.
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Stream erosion and deposition:
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This graph shows the direct relationship between the velocity of a stream and the size of the particles it can transport. The faster the stream flows the larger the particles it can move. On the left is particle diameter, the size in centimeters. The colors show the range of sizes in centimeters.
The colors show the range of sizes that are classified as clay, silt, sand, etc. all the way up to boulders. These size ranges correspond to the values on page 7 for the Grain Size of land-derived sedimentary rocks. Keep this in mind: If a stream is moving fast enough to carry cobbles, it is also carrying everything smaller than cobbles. As it slows down the largest particles drop to the bottom (settle out) first followed by smaller and smaller particles. This is called "sorting" and it can happen vertically or horizontally. regentsearth.com |
When sediments stop being transported and are set down somewhere on Earth's crust, they are said to be deposited. Seen from the chart above, sediments of different sizes are able to stay afloat in different speeds of water. A bigger sediment like a boulder needs very fast moving water whereas something small like clay can stay afloat in very slow moving water. When sediments are set down in water they do it in a particular way. Think of carrying groceries from the car into the house: you bring all the bags at once because you don't want to make 2 trips. As soon as you enter the house you set down the heavy bags (the milk, juice, cans, etc.) The lighter stuff you hold onto for longer and bring it into the kitchen. Rivers and streams do the same thing, as soon as the river meets the ocean it slows down resulting in the deposition of the big particles, like boulders. It then drops off the pebbles, then the sand, silt and finally the clay. This is called sorting and it can look horizontal or vertical depending on the situation.
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Vertical Sorting and Graded Bedding:
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Oxbow lake, small lake located in an abandoned meander loop of a river channel. It is generally formed as a river cuts through a meander neck to shorten its course, causes the old channel to be rapidly blocked off, and then migrates away from the lake. If only one loop is cut off, the lake formed will be crescent shaped, whereas if more than one loop is cut off, the lake will be serpentine or winding. Eventually, oxbow lakes are silted up to form marshes and finally meander scars, marked by different vegetation or the absence of cultivation. The lakes commonly are filled with clay-sized sediment that is less easy to erode than surrounding material and thus may cause a more complex meandering system in its parent stream. (Encyclopedia Britannica)
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Click below for an animation of oxbow lake formation
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