BELLWORK Name the 3 types of plate boundaries and an example of each.

Deforming the Earth’s Crust

Moving Continents

Tracking Tectonic Plates Scientists use GPS to track plate movement. Radio waves are beamed from satellites to GPS ground stations which record their position.

3 Possible Driving Forces Convection Currents Ridge Push and Slab Pull –Ridge Push – At mid-ocean ridges, the oceanic lithosphere is higher than it is where it sinks into the asthenosphere. Because of ridge push, the oceanic lithosphere slides downhill under the force of gravity. –Slab Pull – Because oceanic lithosphere is denser than the asthenosphere, the edge of the tectonic plate that contains oceanic lithosphere sinks and pulls the rest of the tectonic plate with it in a process called slab pull.

Plate movement causes geological events such as mountain formation, volcanic eruptions, and earthquakes.

Deformation The process by which the shape of a rock changes because of stress. –Stress is the amount of force per unit area on a given material. Different things happen to rock when different types of stress are applied. –Rock layers bend when stress is placed on them. –When enough stress is placed on rocks, they can reach their elastic limit and break.

Compression The type of stress that occurs when an object is squeezed, such as when two tectonic plates collide. When compression occurs at a convergent boundary, large mountain ranges can form.

Tension Stress that occurs when forces act to stretch an object Tension occurs at divergent plate boundaries, such as mid-ocean ridges, when two tectonic plates pull away from each other.

Folding The bending of rock layers because of stress in the Earth’s crust. Types of Folds – depends on how the rock layers deform: –Anticlines –Synclines –Monoclines

Anticline Upward- arching folds. Caused by horizontal stress.

Syncline Downward, troughlike folds. Caused by horizontal stress.

Monocline Fold where both ends are horizontal. Cause by vertical stress.

Faulting The surface along which rocks break and slide past each other. –Some rock layers break when stress is applied –The blocks of crust on each side of the fault are called fault blocks.

Footwall & Hanging Wall When a fault is not vertical, its two sides are either a hanging wall or a footwall.

Normal Fault When a normal fault moves, it causes the hanging wall to move down relative to the footwall. Caused by rocks being pulled apart (tension).

Normal Fault

Reverse Fault When a reverse fault moves, it causes the hanging wall to move up relative to the footwall. Caused when rocks are pushed together (compression).

Reverse Fault

Strike-Slip Fault When opposing forces cause rock to break and move horizontally.

Mountain Building When tectonic plates undergo compression or tension, they can form mountain ranges in several ways.

Folded Mountains The highest mountains in the world are formed when rock layers are squeezed together and pushed upwards to form folds. –This occurs at convergent boundaries where plates collide. –The plates buckle and thicken. –The continental crust is pushed upward, forming mountains.

Examples of Folded Mountains Himalayas

Alps In central Europe

Ural Mountains in Russia

Great Smoky Mountains

Fault-Block Mountains Form when large blocks of the Earth’s crust drop down relative to other blocks. Tension produces mountains that have sharp, jagged peaks.

Examples of Fault-Block Mountains Teton Range in Wyoming.

Sierra Nevada mountain range in California

Harz Mountains in Germany

Volcanic Mountains Form when magma rises to the Earth’s surface and erupts.

Examples of Volcanic Mountains Mount St. Helens in Washington

Mount Pinatubo in the Phillipines

Uplift and Subsidence Uplift is the rising of regions of the Earth’s crust to higher elevations. –Rebound – When the crust slowing springs back to its previous elevation, as when a glacier melts. Subsidence is the sinking of regions of the Earth’s crust to lower elevations. –Rocks that are hot take up more space than cooler rocks.

Tectonic Letdown Subsidence can also occur when the lithosphere becomes stretched in rift zones.

Quiz 1.Name the 3 types of faults. 2.Name the 3 types of folds. 3.What is compression? 4.What is tension? 5.Would you find a folded mountain at a mid-ocean ridge? Why or why not?