Standards: 3a. Know features of the ocean floor (magnetic patterns, age, and sea floor topography) provide evidence of plate tectonics. 3b. Know the principal structures that form at the 3 different kinds of plate boundaries. 3d. Know why & how earthquakes occur & the scales used to measure their intensity & magnitude. 3e. Know there are 2 kinds of volcanoes: 1 with violent eruptions producing steep slopes & 1 with voluminous lava flows producing gentle slopes. 3c. Know how to explain the properties of rocks based on the physical & chemical conditions in which they formed, including plate tectonic processes.

Earth’s Interior & Plate Tectonics

Earth’s Layers CRUST – topmost layer made of hard, solid rock. Continental Crust – less dense & thicker Oceanic Crust – more dense & thinner

Earth’s Layers MANTLE – layer beneath the crust Makes up about 80% of Earth’s volume Inside is “plastic” – it’s soft and deforms easily (like gum)

Lithosphere The crust & upper part of the mantle About 100 km thick

Asthenosphere Layer of mantle below the lithosphere that consists of slowly flowing solid rock

Earth’s Layers CORE – Center of Earth composed of Iron & Nickel Outer Core – liquid metal Inner Core – solid metal

Alfred Wegener South America & Africa fit together. Found fossils of the same organisms on both continents Ignored, how did continents move?

Plate Tectonics Lithosphere is made of 7 large pieces and many smaller pieces called tectonic plates These plates fit together like a jigsaw puzzle and move in relation to one another

Plate Movement Plates move due to CONVECTION in the asthenosphere As rock gets hot it is less dense and moves up, as it cools off it becomes more dense and falls Like a lava lamp!

DIVERGENT PLATE BOUNDARIES Two plates are moving APART Causes magma to rise and cool, forming more lithospheric rock

Mid-Oceanic Ridges Mountain ranges that form at divergent boundaries Called Ridges Example: Mid-Atlantic Ridge

CONVERGENT PLATE BOUNDARIES Two plates move towards each other CONTINENTAL – CONTINENTAL PLATES Creates MOUNTAINS Appalachians (old) Himalyas (young)

SUBDUCTION ZONES OCEANIC – CONTINENTAL PLATES SUBDUCTION = denser plate goes under less dense plate Dense plate is destroyed & the magma rises to create volcanic island arcs The subducting plate also creates a trench

Examples: Aleutian Islands & Japan

TRANSFORM FAULT BOUNDARIES Two plates break and scrape past one another Cracks where they move are called faults Cause earthquakes Ex: SAN ANDRES FAULT

Evidence for Plate Tectonics MAGNETIC PATTERNS There are “bands” of rock on the ocean floor with alternating magnetic polarities Earth’s magnetic field reverses (200,000 yrs)