Pages in this set

Page 1

Preview of page 1
PLATE TECTONICS

Structure of the Earth

CORE:
Approximately the size of mars and is the densest part of the planet.
Made of rocks rich in iron and nickel.
A semimolten outer core contains a solid inner core of over 6,000 °C.

MANTLE:
Silicate rocks rich in iron and magnesium.
Most…

Page 2

Preview of page 2


Theory of Plate Tectonics

People noticed that continents fitted together.
Geologist Alfred Wegener published his theory in 1912 that all the continents were
once joined together.
He named this ancient supercontinent Pangaea.
Wegener proposed that at some time the land masses had drifted apart until they
occupied their current positions…

Page 3

Preview of page 3

SEA FLOOR SPREADING:
Surveys recorded very young ages for places near or on the ridges.
This is because older crust is continuously being pushed aside by new crust.
This raised a new issue there was no evidence to suggest the earth was
growing in size.
Therefore, ocean crust must be…

Page 4

Preview of page 4
Where spreading occurs beneath a major land mass, the valley sides move
apart.
As this happens, the central sections drop down to form rift valleys.

Destructive Plate Boundaries

OCEANIC ­ CONTINENTAL PLATE CONVERGENCE:
Oceanic crust is subducted because it is denser than continental crust.
As the oceanic crust descends, friction…

Page 5

Preview of page 5
Occurs where two plates are moving in parallel directions.
No crust is destroyed or created although these are areas of frequent seismic
activity because of a high buildup of friction as the plates pass each other.

HOT SPOTS:
Most volcanoes are at destructive and constructive plate boundaries.
However, others do…

Page 6

Preview of page 6
FISSURE ERUPTIONS:
Occur where elongated cracks in the crust allow lava to spill out over a large
area.
Typically these are found around spreading ridges when tension pulls the
plates apart.
Basaltic rock and lava type.
Gentle, persistent eruptions.







SHIELD VOLCANOES:
Basaltic rock and lava type.
Less viscous lava.
Gently…

Page 7

Preview of page 7
ACID / DOME VOLCANOES:
Steep sided volcanoes formed from very viscous lava.
As the lava cannot travel far, it builds up convex coneshaped volcanoes.
Also, lava can solidify in the vent and be revealed later by erosion.
Rhyolitic rock and lava type.
Found on continental crust.
Explosive and unpredictable.







CALDERAS:…

Page 8

Preview of page 8

Minor Extrusive Features

GEYSERS:
Develop when groundwater held in rocks is heated by underlying rocks at
temperatures well above boiling point.
As this water rises towards the surface it dissolves silica from the surrounding
rocks and lines rock crevasses.
This creates a complex underground plumbing system of pipes and
reservoirs.…

Page 9

Preview of page 9

Major Intrusive Features

BATHOLITHS:
Formed by huge masses of magma that cooled slowly within the Earth's crust.
Subsequent erosion stripped away the overlying rocks exposing part of the
igneous mass at the surface.
Because batholiths compromise hard, resistant rock, they form upland areas.
Bosses are the same as batholiths but…

Page 10

Preview of page 10







Impact of Eruptions

Human impacts can be affected by the following:
Exposure. The scale and frequency of the natural event and the number of
people in an affected area.
Vulnerability. The preparedness of a country or population to cope with a
hazard.

Physical impacts can be affected by the following:…

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all resources »