Compressional Forces & Plate Tectonics PDF
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Uploaded by PromisedGuqin
Pretoria High School for Girls
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Summary
This document presents a lecture or presentation on geological topics, specifically compressional forces like folding and faulting, and the formation of different landforms like mountains and rift valleys, and the concept of isostasy. It covers various types of faults and mountain ranges, including young and old fold mountains and the associated areas.
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Compressional Forces Warping Folding Faulting Folding ◆ Occurs along convergent plate boundaries. ◆ Himalayas ◆ Deep layers of sedimentary rock laid down between the plates are squeezed and bent. Himalaya Mountains Fold Mountain...
Compressional Forces Warping Folding Faulting Folding ◆ Occurs along convergent plate boundaries. ◆ Himalayas ◆ Deep layers of sedimentary rock laid down between the plates are squeezed and bent. Himalaya Mountains Fold Mountain Ranges Young Fold Mountains ◆ Found along plate boundaries. ◆ Formed 35 million years ago. ◆ Very rugged, steep slopes , deep valleys and very high ( 6000 m ) Old Fold Mountains ◆ Not on plate boundaries. ◆ 250 million years old. ◆ Formed when the continents were joined. ◆ Eroded for longer. ◆ Lower in altitude and less steep than young fold mountains. Areas between the Fold Mountains ◆ Shields : stable areas, where there has been very little earth movement. They are flat areas. ◆ Plateaus : Flat high lying areas. ( African Plateau ) ◆ Basins : between the shields and the fold mountains. Called lowlands. The nature of Fold Mountains ◆ Symmetrical Fold ◆ Asymmetrical Fold ◆ Overfold ◆ Overthrust Fold ◆ Parts of a fold: limb, anticline and syncline Folds Isostasy ◆ Long periods when mountains are eroded and weathered and material is deposited on the sea-bed. ◆ This causes a redistribution of weight on the surface of the earth. ◆ The balance between the continents and the sea- bed must be maintained. Maintain the balance ◆ Erosion of the continent leads to less pressure on the mantle beneath the continent. ◆ Weathered material deposited on the sea-bed cause more pressure on the mantle beneath the sea-bed. Slow movement of balance ◆ Movement of material from beneath the sea-bed to below the continents. ◆ Mantle : plastic material that can move. ◆ The continent rises and the sea-bed sink slowly. Faults ◆ In unstable parts of the earth the crust is subjected to TENSION and COMPRESSION forces. ◆ When they crack or break it is called a FAULT. ◆ Fault line : the line along the surface where the break has occurred. San Andreas Fault Types of faults ◆ Normal Fault : tension forces (apart) / rocks are thrown down. ◆ Reverse fault : compression forces ( together ) / rocks are pushed up. ◆ Tear fault : tearing forces ( past ). Normal Fault Reverse fault Tear Fault Block mountains and rift valleys ◆ Faults usually occur in groups. Rift valleys
