Earth’s Geology – 3 primary layers Core, Mantle, and Crust Inner core is solid metal (iron and nickle) Outer Core is molten metal Rocky mantle (solid silicate) Molten upper mantle (athenosphere) Crust – thin silicate rock (lithosphere)

Earth’s Crust has ~15 major plates ctonics.html

Convection currents cause plate tectonics. Plates move 2-15 cm per year – about the rate your fingernails grow!

Breaking News – July 2011 Scripps Researchers Discover New Force Driving Earth's Tectonic Plates 'Hot spots' of plume from deep Earth could propel plate motions around globe Scripps Institution of Oceanography / University of California, San Diego

At least twice the landmasses have joined to form a “supercontinent”. Pangea existed about 220 mya

Pangea to today - Animation Choose the AVI and step it along.

divergent, transform, and convergent. Three types of plate boundaries: divergent, transform, and convergent.

Divergent plate boundaries Two plates move apart as magma (liquid rock) rises upward to create new lithosphere.

Divergent plates - Mid-Atlantic Ridge.

Spreading oceanic plates result in formation of new crust on the ocean’s bottom (“seafloor spreading”) and subduction of heavier oceanic plates beneath less dense continental plates.

Mid atlantic ridge – a giant undersea mountain range, started forming 20 million years ago as Africa and S. America separated.

Transform plate boundary Generate earthquakes – eg. San Andreas Fault

Do the Math If two cities lie on different tectonic plates, and those plates are moving so that the cities are approaching each other, how many years will it take for the two cities to be situated adjacent to each other? Los Angeles is 630 km (380 miles) southeast of San Francisco. The plate under Los Angeles is moving northward at about 36 mm per year relative to the plate under San Francisco. Given this average rate of plate movement, how long will it take for Los Angeles to be located next to San Francisco?

Convergent plate boundaries If oceanic and continental plates converge – one plate is subducted and leads to volcanism. – eg. Japan, Mariana Trench, Cascades Mtns, Andes Mtns.

Continental-continental convergence – Himilayas and Appalacian Mountains

GEOLOGIC HAZARDS Earthquakes Volcanoes shaking and release of energy along tectonic plate boundaries. Animation showing cumulative earthquakes Video va/earth/earthquake- detection.html va/earth/earthquake- detection.html when molten rock, hot gas, or ash erupt through Earth’s surface. Form at divergent plate boundaries and subduction zones, and over hot spots. Video – Ring of Fire IMAX

Volcanoes – Hotspots Some “chains of volcanoes” form when mantle passes over a relatively small, long-lasting, and exceptionally hot regions -- called hotspots – that provide localized sources of high heat energy (thermal plumes)

Hawaiian (and Galapagos) islands form from “hotspot”

Figure 8.7 Plate movement over a hot spot. The Hawaiian Islands were formed by volcanic eruptions as the Pacific Plate traveled over a geologic hot spot. The chain of inactive volcanoes to the northwest of Hawaii shows that those locations used to be over the hot spot. Numbers indicate how long ago each area was located over the hot spot (in millions of years).

Yellowstone Volcano progression is evidence for hotspot under mantle.

Plot the data for recent volcanic eruptions on the map on the worksheet – Tectonic Plates Part 1.

Ring of Fire – lots of volcanoes at plate boundaries

Tsunamis can follow earthquakes and volcanos. Dec 26, 2004 Tsunami, triggered by earthquake off Sumatra, killed 228,000 people

Tsunami strikes Northern Japan on March 11 th, 2011 Tsunami followed an Earthquake of magnitude 8.4

GEOLOGIC HAZARDS Earthquakes Volcanoes shaking and release of energy along tectonic plate boundaries. Animation showing cumulative earthquakes Video va/earth/earthquake- detection.html va/earth/earthquake- detection.html when molten rock, hot gas, or ash erupt through Earth’s surface. Form at divergent plate boundaries and subduction zones, and over hot spots. Video – Ring of Fire IMAX

Earthquakes Liquefaction of recent sediments causes buildings of sink Landslides may occur on hilly ground Shock waves Epicenter Focus Two adjoining plates move laterally along the fault line Earth movements Cause flooding in Low-lying areas

Richter Scale