Plate Tectonics….and Your Community

Structure of the Earth

Crust – the thin outermost layer of the Earth. Continental crust is relatively thick and mostly very old. Ocean crust is relatively thin, and always geologically very Young.

Mantle – the zone of the earth below the crust and above the core. It is divided into the upper mantle the lithosphere and lower mantle with transition zone between.

Lithosphere – the outermost layer of the earth, consisting of the earths crust and part of the upper mantle. The behaves as a rigid layer, in contrast to the underlying asthenosphere.

Asthenosphere – the part of the mantle beneath the lithosphere . The asthenosphere undergoes slow flow, rather than behaving as a rigid block, like the overlying lithosphere.

Core – The core is mostly of iron, it is hot. The outer core is liquid and the inner core is solid because of the pressure coming form the earths others layers.

Measuring Plate Motions With GPAGPA

It stands for Global Positioning System satellite based system for accurate location of points on the earth. The good thing about GPA give the accurate rate of movement that plate move over time. The horrible thing is that GPA have only been around for the last ten years. GPA sends a message's to local station around the such as the WES2, or the LMNO station and more. Most all plate are moving so they can be monitored by GPA and you can’t watch a plate move with your eyes it takes a long time.

Plate Boundaries A. Divergent Plate Boundary – a

plate boundary where two plates move away from one another

B. Convergent Plate Boundary - a plate boundary two plates move toward each other.

C. Transform fault - a plate boundary where two plates slide parallel to one another

Divergent plate boundary can cause rift valley formation. Like in Africa the Nile River.

There are a couple of convergent boundary such as ocean-continent, or ocean to ocean, or continent to continent. Like the Nazca plate and the South American Plate.

The North American plate and Pacific plate are move the same direction.

The Mid-Ocean RidgeThe mid ocean ridge – chain of undersea ridges extending throughout all of the earths ocean basins, and formed by sea floor spreading.

The main rock in the ocean is Basalt-a kind of volcanic igneous rock, usually dark colored, with a high content of iron

Every time it spreads it changes its magnetic field form normally or positive, and reversed or negative as you see the picture on the right.

This is how the ocean basin changes its size.

SubductionThe movement of one plate downward into the mantle beneath the edge of the other plate boundary at a convergent boundary the down going plate always is oceanic lithosphere. The plate the stays at the surface can have either oceanic lithosphere or continental lithosphere.

Evidence for Earths Layered Structureo Density is the mass per unit volume of a material or substance.o To find the volume the equations is F= gm 1 gm 2 / by D2 as where m1 and m2 stand

for masses of two objects -d for distance and- g for gravitational constanto Or as we did in class D= mass / by volumeo The outer core and part of the mantle are liquids but the in core is a solid because of

all the heat and pressure coming form the crust, mantle and outer core.o The temperature of the earth increases with the depth. The temperature affects the

density of materials.o

Layer Thickness

Composition Temperature

Density

Cont-Crust 30-60 Granitic 60% silica

20-600 -2.7

Ocean- Crust

5-8 Basaltic 50% silica

20-1300 -3.0

Mantle 2800 Solid Silicate 100-3000 -5

Outer-Core 2150 Liquid Iron 3000-6500 -12

Inner-Core 1230 Solid Iron 7000 -12

Thermal Convection A pattern of movement in a fluid caused by heating form below and cooling from above. Thermal convection transfers heat energy from the bottom of the convection cell to the top.

This is just like balloons when hot air balloons rise but when they get denser and denser the drop just like the inside when they are heated by the outer core they rise later they cool and become less dense that's is when it inks back into the lower part of the mantle the Asthenosphere.

Building Features On Earths Surface

The valley that is formed above the zone of bending is called a trench . They are very deep were only some submersibles can go.Volcanoes are also know to be in the ocean called volcanic arcs. Volcanoes can also form under hot spots. The material rises form outer core to the surface. Did you know that most mountains for on convergent plate boundaries.Growth of continents at Subduction zone is called continental accretions is the growth of continent along its edges.A transform fault may cause earthquakes when the rock are sliding and have been together for a long time.

Development of the Plate Tectonics Theory There are two plate theory's. The first was developed by a an

Austrian geological named Eduard Seuss said that the earths cooled from a molten state, the more dense materials contracted and sank toward the center, the least dense material floated and cooled to from the crust.

Not all geologist accepted the theory of Mr. Eduard. Mr. Alfred Wegener theory was continental drift. This theory said that once there was a land called Pangea billions of years ago and start breaking apart till morden day and is still moving apart.

Paleomagnetism – the record of the past orientation and polarity of the earths magnetic field recorded in rocks containing the minerals magnetite.

Supercontinent – a large continent consisting of al of the earth continental lithosphere. Supercontinents are assembled by plate tectonic processes of Subduction and continent- continent collision.

PangeaEarths most recent super continentWhich was rifted apart about 200 million years ago.

The EndBy Mobert

Email me my grade please