Tectonic boundaries and hot spots
A useful reference dynamicearth/sitemap.html ynamic.html#anchor
Types of Plate Boundaries Divergent - Pull apart- Mid Ocean Ridges Convergent- Come together- subduction zones- Andes Mts. Transform- sliding past each other- San Andreas fault zone California
The all inclusive Plate boundary picture
Volcanoes Mid Ocean volcanoes Mostly basaltic Source of magma is hot mantle area. Shield type volcanoes Continental Margins and Island Arcs Source of Magma is mostly remelting of pre- existing rocks, through the continental crust, producing Andesite and Rhyolite lavas Stratovolcanoes
Earthquakes Earthquake locations are used to determine the plate boundaries. Plates are the large pieces of the earth that have few earthquakes, the boundaries are where the earthquakes occur because this is where the blocks of the earth are interacting with each other, pushing into each other, sliding past each other
Tectonic boundaries and hot spots
Mid-ocean Ridges with Transform Faults The orientation of Transform faults help to determine plate motion direction. These have shallow earthquakes
Trenches at Island Arcs These have shallow to deep earthquakes and usually rhyolitic flows
The west coast shows aspects of both subduction in the north and transform motion in the south
The Formation of granitic bodies as a result of subduction and melting of surface rocks
Erosion of the Earth’s surface exposes these granitic bodies
Major locations of granitic bodies in the North America
The Plate Boundaries with the motion of the plates indicated by arrows
Convective heat flow from inside the Earth is the ultimate cause of volcanoes, earthquakes, and plate motion. When the Earth cools completely –no more volcanoes etc.
Earthquake Waves There are three types of seismic waves that travel through and on the earth –P waves - Compressional travel about 6 km/sec Travel trough both solids and liquids –S waves – Shear waves travel about 4 km/sec Travel only through solids (not the liquid outer core) –Surface waves- travel only along the surface at about 3.5 km/sec
Seismic Body Waves
Shadow Zones… How do we know how big the liquid core is?
Interior of the Earth The earth’s interior is divided into Crust 0-35 km Mantle km Outer Core km Inner Core km From Earthquake studies Also: Lithosphere km Asthenosphere km Based on rigid vs. plastic
HOT SPOTS OF THE WORLD
Hot spots can show the direction of plate motion
Problems Not solved Driving Mechanism Why Hot Spots How deep does convection take place
Driving forces :Convection, Slab pull, Ridge push
Some mineral locations of North America
Types of mountains or mountain ranges Volcanic- West coast –Mt. Rainer Fault, trusting – Western U.S. Basin and Range area- Nevada Folded – Appalachian Mts. Eastern Pa, West Virginia etc.
USA Relief Map
Pennsylvania - folded ridge and valley area
Metamorphic region of Eastern U.S,
Wisconsin Tectonic History 1
Wisconsin Tectonic History 2
Wisconsin Tectonic History 3
Igneous Adirondacks NY
Typical compass for class use
Direction a compass points in U.S.
Earth’s Dipole Magnetic Field
Reversal of the Earth’s magnetic Field Present world - arrows in at North Reversed field – arrows out at North
Before 500 years before middle of reversal Middle of reversal 500 year after middle of reversal
Example evidence from Igneous rocks: Lava flows and sea floor magnetic anomalies
Comparison of Polar wander curves
Wisconsin Aeromagnetic map
The complex geologic tectonics of the Midwest