Light Light refreshments refreshments beforehand!beforehand!

Plate Tectonics - Part IIPlate Tectonics - Part II((What ELSE can happen??What ELSE can happen??))

I.I. The Appalachian Mountains are a product of The Appalachian Mountains are a product of ancient subduction followed by collisions. ancient subduction followed by collisions.

The giant folds in the rocks that The giant folds in the rocks that are so visible in the satellite are so visible in the satellite images are also readily available images are also readily available from the window of a plane.from the window of a plane.

Other bits and Other bits and pieces of land - pieces of land - islands and the islands and the like - can also get like - can also get caught up in the caught up in the convergent plate convergent plate process.process.

This is what creates This is what creates what are now what are now recognized as recognized as accreted terranesaccreted terranes, , (originally called (originally called ""suspect terranessuspect terranes").").

IMAGINE ... IMAGINE ... what the geologic what the geologic situation would situation would ultimately look ultimately look like if Australia like if Australia

were to be moving were to be moving to the NW, to the NW,

pushing pushing everything from everything from New Guinea to New Guinea to

Sumatra into the Sumatra into the SE margin of the SE margin of the Asian mainland... Asian mainland...

What might the future hold???What might the future hold???

MAYBE!!!!!MAYBE!!!!!The The BASIN AND BASIN AND RANGE ProvinceRANGE Province of of the western U.S., the western U.S., including all of Nevada including all of Nevada and parts of and parts of surrounding states, surrounding states, MAY be an area where MAY be an area where North America is North America is trying to split apart! trying to split apart!

The mantle upwelling The mantle upwelling beneath the East beneath the East Pacific Rise doesn't Pacific Rise doesn't just cease to exist in just cease to exist in between the Gulf of between the Gulf of California and the California and the Gorda Ridge!Gorda Ridge!

This region has been broadly UPLIFTED by tectonic This region has been broadly UPLIFTED by tectonic forces pushing up from beneath.forces pushing up from beneath.

The plains of Wyoming are very The plains of Wyoming are very flat, but 7000-8000 feet (2100 flat, but 7000-8000 feet (2100 to 2400 m) above sea level.to 2400 m) above sea level.

The Grand Canyon catches The Grand Canyon catches the eye for its tremendous the eye for its tremendous depth, but the North Rim is depth, but the North Rim is also over 8000 feet (2400 m) also over 8000 feet (2400 m) above sea level! Note how above sea level! Note how FLAT the upland surface is!FLAT the upland surface is!

In most other areas, the rocks In most other areas, the rocks have fractured in have fractured in normal normal faultsfaults, which are produced , which are produced only by stretching a only by stretching a brittlebrittle material - pulling it apart.material - pulling it apart.

On a larger scale, this On a larger scale, this then shows up in repeated then shows up in repeated patterns of patterns of block faultingblock faulting

The Humboldt Range of The Humboldt Range of Nevada, for example, is part Nevada, for example, is part of this system.of this system.

This produces a series of downdropped This produces a series of downdropped blocks called blocks called GRABENSGRABENS in between the in between the uplifted uplifted HORSTSHORSTS. (The grabens are the . (The grabens are the valleys, the mountain ranges the horsts.)valleys, the mountain ranges the horsts.)

What What COULDCOULD happen as an alternative scenario, happen as an alternative scenario, as a result of this process in the western U.S.?as a result of this process in the western U.S.?

It's thinking about It's thinking about scenarios like this that scenarios like this that

has led some geologists to has led some geologists to call geophysics call geophysics

""The realm of conjecture, The realm of conjecture, speculation and dreams.speculation and dreams." "

Coming Coming Tuesday:Tuesday:

Producing Islands by RiftingProducing Islands by Rifting