Ch. 11 NotesDeformation of the Crust

How Rock Deforms

Earth’s surface changes constantly Isostasy

When lithosphere and asthenosphere are balanced

If weight of lithosphere changes, it sinks or rises until there is a balance again

How Rock Deforms

Stress Force exerted on a rock

as lithosphere moves Types of stress:

Compression – squeezes and shortens

Tension – stretches and pulls

Shear stress – parts pushed in opposite directions

How Rock Deforms

Strain When rock changes its shape or volume

because of stress Stress doesn’t always change a rock, it can

“bounce back”

How Rock Deforms

Folds Bend in rock layers

that results from stress

Result of compression or shear stress

How Rock Deforms

Faults Break in rock where surrounding rock moves Earthquakes occur along fault lines

Mountain Ranges

Mountain ranges believed to be formed by once active tectonic plates Results of collisions between:

Continental and oceanic crust Oceanic crust and oceanic crust Continental crust and continental crust