EXTERNAL CHANGES
- 1. The landscapes change with time. There are 5 agents that produce this change: Wind Rivers Sea Underwater Glaciers
- 2. Weathering: It is produced when the rocks break into smaller pieces. Erosion: The rocks fragments are eroded by the wind, water or ice. Transport: The wind, the water or the ice transport the small fragments from one place to another. Sedimentation: The small fragments are deposited on the soil. They are called sediments.
- 3. The wind transports small particles, and these particles erode the rocks. Example: Desert: In the desert , the wind transports sand. When the wind drops the sand, it forms dunes.
- 4. The rivers also change the landscapes. The rivers have 3 parts: a) High course: the rivers start at the high course. The current is very fast, and the inclination is big. In the high course, there is High Course weathering, erosion and transport. b) Middle course: the current is not so fast because the inclination is smaller. In the middle course, there is erosion, transport and sedimentation. c) Low course: the river arrives at the sea. The current is very slow because there is no inclination. In the low course, there is transport and sedimentation of the small fragments. Sometimes, in the low course the rivers form a delta. Low Course Middle Course
- 5. The waves of the sea erode the costs and cliffs. Cliffs change their shape: 1. The waves erodes the low part of the cliff. 2. The high part of the cliff starts to break. 3. The fragments of cliff fall into the sea. Very slowly the waves erode this fragments. 4. The sea deposits the sediments on the beaches. These sediments come from: the rivers and the cliffs.
- 6. When it rains, part of the water filters in the soil. The underwater changes the underground. It forms caves, and these caves have stalactites and stalagmites.