geography revision 2014 no 3

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TECTONICS/RESTLESS EARTH-

definition of tectonics-the study of the make up of the earth and how people are affected by it.

structure of the earth-in to out-inner core-outer core-mantle-crust.

lithosphere-the crust and the rigid top layer of the mantle.

characteristics of each layer of the earth-inner core-the centre and the hottest part of the earth, it is solid and made up of iron and nickel with temperatures of up to 5500 degrees Celsius. with its immense heat energy the inner core is like the engine room of the earth.

the outer core-is the layer surrounding the inner core, it is a liquid layer, also made up of iron and nickel, it is still extremely hot with temperatures similar to the inner core.

the mantle-is the widest section of the earth. it has a thickness of approximately 2,900 km. the mantle is made up of semi molten rock called magma. in the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.

the crust-is the outer layer of the earth it is a thin layer between0-60km thick, the crust is the thin rock layer upon which we live. there are two different types of crust: continental crust which carries land and oceanic crust which carries water.

convection currents: the earths crust is divided into tectonic plates which float on the upper layer of the mantle. heat from the is caused by radioactive processes. warmer magma closer to the core becomes less dense and rises and as it rises it get further away from the core and cools, the cooler magma sinks this creates a circular motion which pushes the plates around the earth. see book for diagram.

evidence for continental drift is: the same types of fossilised animals were found in Africa and south America suggesting that the two countries had once been joined.

-the shape of the east coast of south America fits the west coast of Africa like pieces in a jigsaw puzzle, this is the case for some other countries as well.

-matching rock formations and mountain chains are found in south America and Africa.

distribution of earthquakes and volcanoes worldwide- earthquakes and volcanoes usually form or happen between tectonic plates and on rare occasions they can happen between fault lines so if you're no-where near a tectonic plate line then you are pretty much safe.

names of major tectonic plates are - the Pacific plate, the north American plate, the Nazca plate, the south American plate, the African plate, the Eurasian plate, the indo Australian plate, the Antarctic plate, see book to see where they are (seriously).

properties of different tectonic plates-

-oceanic plates-newer-most less than 200 million years old, denser, can sink, can be renewed and destroyed.

-continental plates-older-most over 1500 million years old, less dense, cannot sink, cannot be renewed or destroyed.

the four types of plate boundary-

-subduction zone-where a continental and an oceanic plate collide because of the differences in density the oceanic plate is forced under the continental plate, as subduction occurs heat is generated and the tip of the oceanic crust may be melted away creating a pool of extra magma which forces its way to the surface and erupts as a volcano earthquakes also happen at his type of zone when the pate collide frequently.

-collision zone-this is where two continental plates meet, neither plate goes underneath other and so they collide causing pressure to be released and sometime violent earthquakes to happen this pressure also causes the formation of huge fold mountains. there are no volcanoes for this type of plate margin.

-conservation zone-this occurs when two plates move past each other in different directions or a different speeds.as the plates move past each other they jam and pressure builds up, this pressure is released causing frequent and violent earthquakes, there are no volcanoes for this type of plate margin.

constructive zone-where two plates (oceanic or continental) move apart, convection currents move them apart, hot magma rises as they separate the magma cools and forms new crust, there is gentle volcanic activity at these plate margins.

types of volcano and what plate boundary they occur at-composite cone volcano-occurs at a subduction zone destructive plate boundary.

shield volcano-occurs at a constructive plate boundary.

classifying volcanoes-

active-still active and erupt frequently

dormant-temporarily inactive but not fully extinct.

extinct-never likely to erupt again.

labelling a volcano-looking on internet or in book for a diagram of a volcano.

characteristics of composite cone and shield volcanoes-

composite cone volcano-

-tall cone narrow base, steep sides.

-alternate layers of lava and ash

-irregular eruptions and long dormant periods

-violent explosions possible

-lava is sticky and doesn't flow far

-lava is acidic

-also called a strata volcano.

shield volcano-

-made of lava only

-wide base and gentle slopes

-regular and frequent eruptions

-lava pours out with little violence

-lava is basic (opposite of acidic)

-lava is runny and flows a long way.

examples of composite cone volcanoes-Krakatoa in Indonesia

-Etna, Vesuvius and Strombolia in Italy.

examples of shield volcanoes-

-Hekla and Surtsey in Iceland

-Mauna Loa and Kilauea in Hawaii.

Montserrat read two pages of textbook.

19 people died in the main eruption

you could still catch a lung disease called silicosis due to a certain type of quartz left behind by the volcano.

volcano caused by Atlantic plate (oceanic) sinking under Caribbean plate (continental)

Plymouth buried airport and vital infrastructure destroyed, homes destroyed.

more than half the island made uninhabitable.

economy devastated.

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