2. The theory of plate tectonics states that the earth is made up
of a number of layers.
On the outside there is a very thin crust and underneath is a
mantel which makes up 82% of the volume of the earth.
Deeper still is a very dense and very hot core.
3.
4. The past and present
distribution of
earthquakes.
The fit of the continents.
Glacial deposits in Brazil
match those in West
Africa.
The fossil remains in India
match those found in
Australia.
Fossil remains of a small aquatic reptile, which is a poor
swimmer, are found only in Brazil and southwest Africa.
7. The zone of earthquakes around the world has helped to
define six major plates and a number of minor ones.
There are three main types of boundaries:
• Constructive margins (divergent)
• Destructive margins (convergent)
• Conservative or passive margins (transform)
8.
9. Also known as spreading or divergent plates.
Two plates move away from each other, new oceanic crust is
formed, resulting in mid-oceanic ridges with volcanoes.
Associated with these margins are shallow earthquakes (less
than 50km below the surface).
Examples:
Mid-Atlantic Ridge (Americas moving away from the
Eurasian and African Plates).
East Pacific Rise (Nazca and Pacific Plates moving apart).
East African Rift and Valley and Red Sea.
10.
11.
12. Oceanic crust moves towards continental crust, but, being
heavier sinks and is destroyed forming deep-sea trenches
and island arcs with volcanoes.
Examples:
Nazca sinks under South American Plate (Andes).
Juan de Fuca sinks under North American Plate (Rockies).
Island Arcs of the West Indies.
13.
14.
15. Transform boundaries (Conservative) occur where two
lithospheric plates slide, past each other along transform
faults, where plates are neither created nor destroyed.
The relative motion of the two plates is either sinistral (left
side toward the observer) or dextral (right side toward the
observer).
Transform faults occur across a spreading centre. Strong
earthquakes can occur along a fault.
Examples: The San Andreas Fault in California is an example
of a transform boundary.
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24. Research at home, and summarize in your books, at the end of the
lesson, in one two paragraphs one strong earthquake and the type of
plate boundaries (and boundaries involved (one paragraph is at least
three sentences).