Plate Tectonics

The Earth’s crust consists of a number of plates which are in motion (quite slow)

The Layers of the EarthEarth

The movement of crustal plates results from convection currentsconvection currents in the MantleMantle. Heat from the formation of the Earth and radioactive decay escapes at the Earth’s surface.

Some plates contain mainly oceanic crustmainly oceanic crust and some contain both both continentalcontinental and and oceanicoceanic crust crust.

Bullard Fit of Continents.swf

Shortcut to Bullard Fit of Continents

The Glomar Challenger was the first research vessel specifically designed in the late 1960s for the purpose of drilling into and taking core samples from the deep ocean floor.

Remote SensingRemote Sensing- uses energy signals from Earth to determine many different kinds of information

Earthquake Zones

EarthquakeEarthquake and VolcanoVolcano Activity closely matches the plate boundariesplate boundaries!

Mid-Ocean Ridges

Computer-generated detailed topographic map of a segment of the Mid-Oceanic Ridge

Sea Floor Spreading.swf

Shortcut to Sea Floor Spreading Shortcut to Formation of Ocean Crust

There is evidence of “Sea floor spreading” on either side of the Mid-Atlantic Ridge

Divergent boundariesDivergent boundaries occur along spreading centers where plates are moving apartmoving apart and new crust is created by magma magma pushing up from the mantlepushing up from the mantle.

IcelandIceland is right on an oceanic-oceanic-

oceanicoceanic Divergent Divergent Plate Plate BoundaryBoundary

plate boundaries.swf

Plate Boundaries

Convergent boundariesConvergent boundaries are where plates are moving

toward each othertoward each other, and sometimes one plate sinks (is subductedsubducted) under another.

The location where sinking of a plate occurs is called a

subduction zonesubduction zone. subduction

HeatHeat from friction melts rock and the magmamagma forms volcanoesvolcanoes

Mount Baker (Washington)

Mount Rainier (Tacoma in

foreground)

Deep trenchestrenches are formed in the ocean floor where subduction begins

Oceanic-oceanic convergent Oceanic-oceanic convergent boundariesboundaries produce volcanic Island Island Arc’sArc’s

They also produce a trenchtrench

An oceanic-oceanic oceanic-oceanic convergent boundaryconvergent boundary.

Where might we find trenches?

The Mariana Trench is the deepest known trench.

The bottom of the trench (Challenger Deep) is further below sea level than Mount Everest is above it. The trench has a maximum depth of 10,911 10,911 m (35,798 feet) below sea level.

Continental-continental Continental-continental Convergent plate boundariesConvergent plate boundaries can produce mountain ranges.mountain ranges.

The zone between two plates sliding horizontally past one horizontally past one anotheranother is called a transform-transform-fault boundaryfault boundary, or simply a transform boundarytransform boundary.

Transform BoundariesTransform Boundaries

Shortcut to Transform Faulting.lnk

transform faulting

Some Transform Transform BoundariesBoundaries

The San San Andreas FaultAndreas Fault

Measuring displacementdisplacement in a small transform fault

Remote sensingRemote sensing from satellites can detect small movements on either side of a fault.

In Transform BoundariesTransform Boundaries, no new crust is formed and no crust is destroyed. EarthquakesEarthquakes often occur along transform boundaries.

Hot Spot VolcanoesHot Spot Volcanoes

Hot Spot Hot Spot VolcanoesVolcanoes are

notnot at plate boundaries

Oceanic CrustOceanic Crust moves over fixed fixed hot spot.hot spot.

Hot Spot Volcanoes.swf

hot spot volcanoes

The oldest oldest volcanic island is farthestfarthest from the hot spothot spot in the direction of the plate direction of the plate movementmovement.

Eroded volcanic islands which are below the surface are called SeamountsSeamounts

The trail of underwater mountains created as the the tectonic plate moved across the Hawaii hotspot over millions of years, known as the Hawaiian-Emperor seamount chain, or the Emperor Seamounts (Which direction do you think the Pacific Plate is moving?)

Mauna Loa, comprising over half of the Big Island, is the largest shield volcano on the planet. The measurement from the base locally depressing the sea floor in the Hawaiian Trough to its peak is about 17 km (56,000 feet) Sea Level to peak of Everest is 8,848

meters (29,028 feet)