summary 2.2,3,4,5

Summary Geography

2.2

High-Mountains ranges have a lot of relief, high tops, deep valleys and steep slopes. Enormous mountain top slowly break down. Rock falling apart is called weathering. What causes weathering? (There are several ways)

Mechanical weathering (movement)

• Freeze thaw: there are several cracks and crevices in the rocks. After a rainfall, the water gets in the cracks. At night, the water freezes and expands. Due to this the cracks get larger.
• Onion skin: the sun heats a rock up during the day, while cooling off to bolow freezing at night. This causes the rock to expand and contract. Due to this the rock break into pieces.
• Biological: plants roots, animals and humans break the rock.

Chemical weathering (changes)

• The rock dissolves or changes because of carbon gas.

Caves are formed when water seeps down into the limestone through the cracks. Due to the plants roots, the water becomes a little acid (zuur), dissolving the limestone, and as a result, the caves form.

2.3

Rocks moving down the slope is called mass movement, the major role in this is gravity.

When rocks fall from the mountain tops they fall into the river, they’ll scrub against each other and they’ll form shingle, which are round-shaped rocks. The shingle rubs along the bottom of the river so the river becomes deeper slowly. This is called erosion, running water, wind or ice wearing away the Earth’s surface.

Erosion can be caused by glaciers in the high-mountain ranges. Glaciers are thick packs of ice and it wears away the ground underneath. When the ice moves over the ground, it makes rounded shape. Wind can cause erosion as well when there’s sand in it.

If the scouring of erosion continunos for millions of years, the river creates a deep valley in the mountains. These valleys are V-shaped and are called river valleys.

Weathering and erosion ensure that all the rock crumbles into tiny grains, sand. Grains that can only be seen under a microscope are called clay.

2.4

Sand, shingle and clay are carried by a river, and they get dropped in the lower reaches. This happens when a river has to carry more than its capacity. The water then flows into the flat areas, as long as there no dykes. As the water flows slowly here, or not at all, all the single, sand and clay is dropped. The dropping is called sedimentation. Due to this, low lying areas deltas are formed.

The part of the sand and clay carried by the river is taken away by the current in the sea water. Grain of sand fall to the bottom. They form sandbanks and on the beach as it is. Dunes are formed on the beach, around small plants or beachgrass. They start off small but they become meters high.

When sedimentation has been going on for a long time, the low plains consist of layers of stand and clay, kilometers thick. Those layers are so tightly compressed that the loose sand and clay change into rock. Thus, sand => sandstone, clay => shale and shells => limestone. This rock is formed from compressed sediment is called sedimentary rock. When pieces of rock are drilled up, the layers of sand and clay can still be seen. The rocks also have remains of shell and plants. These remains are called fossils.

2.5

Mountain tops crumble due to weathering and erosion, and lowlands are formed layer-by-lay. This process is very slow.

A young mountain range has only existed of 10 millions of years and old mountain range has existed of hundred million years. Young mountains are taller than old mountains because in young mountain the top hasn’t started with curmbling.

New mountain ranges are formed of layers of rock with fossils and shells that lived in the sea. So it starts on the bottom of the sea. But it becomes a mountain by the collision of tectonic plates. At the places where these plates are colliding, the sedimentary rock is pressed together and pushed up. This is a very slow process, which can take millions of years.

Liquid material was pushed from the Earth’s mantle. This is called magma. Rock that is formed when liquid magma solidifies (stolt, hard worden) is called igneous rock. It is irregular and speckled. An igneous rock of coarse (van grof) grain is called granite. This is much harder than sedimentary rock, so the peaks in the Alps are often from granite.