Plate Tectonics

Layers of the Earth Crust – Rocky outermost layer Approximately 5-40 km Includes the land surface and the ocean floor

Layers of the Earth Mantle – middle layer of hot rock About 80% of Earth’s total volume Lithosphere – rigid layer of crust in the upper mantle Asthenosphere – soft layer below lithosphere Almost 3,000 km thick

Layers of the Earth Core – center which consists of the outer and inner core; made of iron and nickel Outer core – molten (liquid-like) metal Inner core – dense ball of solid metal; about 5,000oC

Some Facts to Know The deeper you go towards the center of the Earth, the greater the temperature and pressure Because scientists cannot study the Earth’s interior directly, they study and record how seismic waves travel through Earth

More Facts Heat from the mantle and core cause convection currents, which are responsible for Earth’s magnetic field

More Facts Forces beneath the surface are constantly changing Earth’s surface TWO TYPES OF FORCES: Constructive – build up land masses and mountains Destructive – wear away mountains and features

Plate Tectonics States that pieces of Earth’s lithosphere (plates) are in constant slow motion, driven by convection currents in the mantle As the plates move, they collide, pull apart, and grind past each other Move at a very slow rate: about 1-10 cm per year

Boundaries Where the plates in the lithosphere meet Three main types of boundaries Transform – two plates slip past each other in opposite directions Where earthquakes occur

More Boundaries 2. Divergent – plates move apart (diverge) Rift valleys form 3. Convergent – plates come together (converge) Collision occurs when the two plates collide; the density of the plate determines which one comes out on top Can cause mountain building

Deformation Stress in rock leads to three types of deformation… Shearing: pushes in two opposite direction Tension: pulls on rock making it thinner in the middle Compression: squeezes rock together making it thicker in the middle

Faults Breaks in the Earth’s crust where plates slip past each other Three main types: Strike-slip Normal Reverse

Strike-slip Fault Caused by shearing Rocks slip past each other with little up or down motion

Normal Fault Caused by tension Fault is at an angle so half the rock lies above (hanging wall) while the other lies below

Reverse Fault Caused by compression Same structure as normal fault, but blocks move in opposite direction

Boundary Stress Fault Movement Transform Shearing Strike-slip Divergent Tension Normal Convergent Compression Reverse