Download The west coast shows aspects of both subduction in the north and

Tectonic boundaries and hot spots
A useful reference
http://www.learner.org/interactives/
dynamicearth/sitemap.html
http://pubs.usgs.gov/gip/dynamic/d
ynamic.html#anchor19309449
Types of Plate Boundaries
• Divergent - Pull apart- Mid Ocean Ridges
• Convergent- Come together- subduction zonesAndes 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 preexisting 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
10-2900 km
Outer Core 2900-5200 km
Inner Core 5200-6000 km
From Earthquake studies
Also: Lithosphere 0-100 km
Asthenosphere 100-700 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