# AIM: Describe the types of stress and the land features (faults,uplift,folds) that result from forces (stress) in the Earth’s crust? OBJ: Given notes.

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AIM: Describe the types of stress and the land features (faults,uplift,folds) that result from forces (stress) in the Earth’s crust? OBJ: Given notes and activity sheet SWBAT describe the types of stress and the land features (faults, uplift, folds) that result from forces (stress) in the Earth’s crust with 70% accuracy DN: Distribute Tectonics Activity Sheet ACT: Introduction to stress, types of stress, fault, kinds of faults and land features (uplift, folding). Text, read p HW: Work on Tectonics Activity Sheet; Tectonics Exam, February 12.

Movement of Earth’s plates creates enormous forces (stress) that pull or squeeze the rocks in the crust. Stress: a force that acts on rock to change its shape or volume. Volume: the amount of space the rock takes up. The stress transfers energy to the rock causing the rock to bend/stretch. But beyond a certain limit, the rock will break.

Types of Stress (Crust)
Occurs over millions of years to change shape and volume of rock. Tension: move apart, stretch rock, divergent motion Compression: come together, squeeze rock, convergent motion Shearing: to move in opposite directions, slip & slide past each other, side by side motion

Fault: a break in rock along which movement occurs (= earthquake)
Fault: a break in rock along which movement occurs (= earthquake). Most faults occur along plate boundaries. Kinds of Faults Normal Fault: caused by tensional forces where plates pull apart (diverge) forming a step-like structure. Reverse Fault: caused by compressional forces where plates come (squeeze) together (converge) forming a “roof shingles” structure. Strike-Slip/Transform Faults: caused by shearing forces where plates move past each other in opposite directions.

Changing Earth’s Surface Over millions of years, the forces of plate movement can change a flat plain into folded mountains, fault-block mountains and plateaus. Folded Mountains: site of collision between two plates. Fold: bends in rock formed by compressional forces that shorten and thicken part of the crust. Anticline: a fold in rock that bends upward into an arch. Syncline: a fold in rock that bends downward to form a valley.

Fault-Block Mountains: where two plates move apart tensional forces can create parallel normal faults. As the plates move apart, the block in between moves upward forming a fault-block mountain.

Horst Graben Graben Graben Horst Horst Graben

Plateaus: a large area of flat land elevated high above sea level formed by uplifting forces in Earth’s crust.

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