How the earth works, Plate tectonics

What makes up the upper mantle

Lithoshpere and asthenoshpere

What is the difference between the lithosphere and the asthenosphere?

Lithosphere- Ridged but can bend under extreme pressure ( upper crust and mantle) Thicker under continental crust and tinner under oceanic

Asthenosphere is under lithosphere and is soft and able to flow.

List the 4 classes of igneous rock and explain why they are different.

Felsic - Least silica- Rhyolite Granite

Intermediate- Andesite Diorite

Mafic- Baslat Gabbro

Ultramafic- Komatite periodotite

These rocks are differentiated based on the amount of silica found in the rock. As silica decreases the amount of iron and magnesium increase.

how do the lithospheric plates behave on the asthenosphere

They ‘float’ as the lithospheric plates are less dense.

What do the earths plates consist of?

Some are entirely oceanic while others are both oceanic and continental.

What is passive basin?

Mechanical thinning of crust that is covered by younger sediment. The top surface creates and continental shelf.

What is an active and margine and passive margine?

Passive means has tectonic activity.

What is a EEZ

Exclusive economic zone, offshore areas in which the bordering country owns all the resources

Where are earth quakes most common?

Tectonic plate boundaries = Seismic belts.

fewer earth quakes in interior as it is more stable.

List 4 basic principals of tectonic plates.

• They move relative to each other, during movement internal areas stay intact as they are ridged.

• Relative movement takes place by slips along plate boundaries

• Continents are part of plates and move with the plates.

• because the plates move the earth is constantly changing.

list the 3 kinds of plate boundreis

Divergent, Convergent and transform.

What is a divergent boundary?

Two plates moving away from each other = sea floor spreading and makes mid-oceanic ridges. Continents move apart.

What is mid-oceanic ridge?

Shallow ridges offset by the transform fault fracture zones

Explain the interior of the MOR

Magma chamber beneath the ridge axis, molten rock flows out to the sea floor and produces basalt pillows. Basalt dikes inject above the magma chamber. Gabbro form deep

Name and example where the plates are moving apart.

Juan de Fuca ridge. The ridge is pulling apart and develops a median valley. Pillow baslat forms at high pressure.

What are black smokers

Chimneys spewing hot mineralized water

how can we tell the age of the oceanic crust.

The youngest crust occurs along the MOR, oldest crust is further from the axis. This is explained by sea floor spreading

where does new lithosphere form?

As two plates move away, dense lithospheric mantle thickens and the sea floor gets deeper. Thickness stay the same as the plate ages.

Explain what occurs at a convergent boundary

Two plates move toward one another. The downgoing plate sinks beneath the overriding plate;

What is a sunduction zone?

The downgoing plate sinks beneath the overriding plate. The Wadati-Benioff zone defines the position of the downgoing tectonic plate above a depth of ~660 km. This is where trenches form

Explain the sinking of the downing plate

similar to that of an anchor. slowly at and angle.

What is a continental volcano arc

Sediments on the downgoing slab are scraped off to form an accretionary prism, and a forearc basin filled with continental sediments form behind the accretionary prism. Continental volcanic arc forms on continental plate behind accretionary prism.

Explain how oceanic island arcs form

When subduction involves two oceanic plates, a volcanic island arc forms on the overriding plate. In some cases, a volcanic island arc develops on a small fragment of continental crust that has split away from the main continent.

Explain what occurs at a transform boundary

At a transform boundary, plates slide past one another along a vertical fault plane.

Name an example of the continental transform crust

San Andreas fault and East Anatolian fault

what is a triple junction?

A triple junction is a place where three plates intersect

what is a hot spot

the consequence of a mantle plume. As the plates drifts over the hot spot it melts and form a chain of extinct volcanoes. eg Hawaiian islands.

What is a seamount and guyot

hot spot volcano eroded and subsided. It sinks below sea level and forms a seamount. Guyot = flat seamount

What are hot spot track used for?

The tracks provide clues to the direction and rate of plate movement. Most recent are at the end of the track.

Explain the process of rifting

When the continental lithosphere stretches and thins, the upper crust breaks by faulting. The upwelling asthenosphere initiates volcanism. Rifting may split a continent in two. an example is the basin and range province (America) and East African rift. red sea was a rift but in now an ocean

Explain what happens when continental crust collide

Continental crust is too buoyant to subduct; when two continents converge, rock undergoes compression and shearing, and a mountain range develops.

what 3 forces drive plates?

Ridge push- gravitational energy associated with topographic elevation

Slab pull- the oceanic crust is denser than the underlying asthenosphere so it sinks

Convection currents are no longer thought to drive plates alone.

how can the motion of a plate be discribed?

Relative (to other plates) and absolute (a fixed point) velocity.

how is plate velocity measured?

Plate velocities can now be measured using global positioning system (GPS) satellites.