Earth Movements

Earth movements are classified into two (2) main groups:

1. Vertical or Radial Movements
2. Lateral or Horizontal Movements (or Tangential)

Vertical or Radial Movements

1. These are the upward and downward movements or forces.
2. These forces cause the uplift (epeirogenic) and the downward movement (cymatogenic).
3. These forces, which cause the vertical earth movements, operate from the interior upward toward the surface or downward from the surface to the interior.
4. Result of Vertical Movement:
   • Changes sea level because of the upward lift of the land or sinking of the land.
   • Note: This change in sea level is not eustatic changes but is due to vertical forces. The eustatic change refers to the changes in sea level due to ice melt during ice ages.

Lateral/Horizontal Movements

1. These are the orogenic forces (movements) because they are part of the process to build mountains.
2. Orogenesis means the process of mountain building.
3. There are two (2) types of lateral forces:
   • Compressional Forces
   • Tensional Forces

1. A rift valley is a trough or hollow, which may result from both vertical and lateral movements of the earth's crust.
2. It is formed when two faults develop parallel to each other.
3. It can develop by either tensional forces or compressional forces.

Formation of Rift Valley by Tensional Forces

1. This is formed when tensional forces move away from each other.
2. These forces of tension produce faults, and the block between two parallel faults subsides to form a rift valley.

Formation of the Rift Valley by Compressional Forces

1. This is formed when horizontal forces act towards each other.
2. These forces of compression produce faults on the outside of the two parallel faults, and the pieces of land on either side are lifted up above the general level of the ground to form a rift valley.

Examples of Rift Valleys

• East African Rift Valley – Africa
• Jordan Rift Valley – Asia
• Rhineland Rift Valley – Europe

1. A block mountain refers to a table-like mountain formed due to the influence of faulting that leads to the rising of crustal rocks.
2. It is nearly a flat surface.
3. Either tensional or compressional forces can form a block mountain.

Examples of Block Mountains

• Usambara and Uluguru, in Tanzania
• Ruwenzori, in Uganda
• Vosges and Black Forest, in Europe
• Mount Sinai, in Asia

1. A plateau is a large, extensive uplifted part of the earth's crust, which is almost flat at the top.
2. The top of the plateau is mostly a plain.
3. Plateaus were formed during Mesozoic and Jurassic eras due to the uplifting of the earth's crust.

1. A basin is a large, extensive depression on the earth's surface.
2. Most basins are formed due to vertical movement of the earth.

Examples of Basins

• Congo Basin
• Chad Basin
• Amazon Basin