Notes for Ch.2-1 Forces in Earth's Crust

Forces in Earth's Crust

Richter Scale used to measure the magnitude of Earthquakes.

How does stress in Earth's crust change Earth's surface?

(Where are faults located?)

Tension, compression, and shearing work over millions of years to change the shape and volume of rock.

Tension: The stress force called tension pulls on the crust stretching rock so that it becomes thinner in the middle. (separated by force)

Tension occurs where two plates are moving apart.

Compression: The stress force called compression squeezes rock until it folds or breaks.

Once plate pushing against another can compress rock like a giant trash compactor.

(Come together)

Shearing: Stress that pushes a mass of rock in two opposite directions is called shearing.

Shearing can cause rock to break and slip apart or to change its shape.

(Move against each other)

Faults location: Majorities of active faults are located along and between tectonic plates.

3 Types of Boundaries:

Convergent boundaries

Divergent boundaries

Transform boundaries

Stress: A force that acts on rock to change its shape or volume.

Most faults occur along plate boundaries, where the forces of plate motion push or pull the crust so much that the crust breaks. There are three main types of faults: Normal faults, reverse faults, and strike-slip faults.

Normal Faults: Tensions in Earth's crust pulls rock apart, causing normal faults. In a normal fault, the fault is at an angle, so one block of rock lies above the fault while the other block lies below the fault.

The block of rock that lies above is called the hanging wall; the rock that lies below is called the foot-wall.

Reverse Faults: In places where the rock of the crust is pushed together, compression causes reverse faults to form. A reverse fault has the same structure as a normal fault, but the blocks move in the opposite direction.

Strike Slip Faults:

In places where plates move past each other, shearing creates strike-slip faults. In a strike slip fault, the rocks on either side of the fault slip past each other side-ways, with little up or down motion.

A strike-slip fault that forms the boundary between two plates is called a transform boundary.

Over millions of years, the forces of plate movement can change a flat plain into land-forms such as anticlines and synclines, folded mountains, fault-block Mountains, and plateaus.

Geologists use the terms anticline and syncline to describe upward and downward folds in rock. A fold in rock that bends upward into an arch is an anticline and a fold in rock that bends downward to form a valley is a syncline.

Anticlines and synclines are found in many places where compression forces have folded the crust.

The forces that raise mountains can also uplift plateaus. A plateau is a large area of flat land elevated high above sea level.

Questions: Big Concept

How does stress in the crust change Earth's surface?

The stress in the crust alters due to faults of volcanoes, mountains, Earthquake.

Where are faults usually found and why do they form?

Majorities of active faults are located along and between tectonic plates.

Faults form by stresses in earth when fractures occur, they are all formed of compression, tension, shearing causes.

What land features result from the forces of plate movement?

The results after the forces of plate movement are land movements or it could last as natural disasters.