CONTINENTAL DRIFT (PHYSICS)

CONTINENTAL DRIFT AND PLATE TECTONIC THEORIES
1)CONTINENTAL DRIFT THEORY
This theory was first conceived by scholars and philosophers like Francis Bacon, George Buffon and Alexander Von Humboldt.
The concept say that the continent once had fit together but has driftted apart after millions years.
Then later later German meteorologist and geophysicist Alfred Wagner (1880-1930).
In 1912 spent much exploration and research to prove the theory of continental drift,
According to his theory” About 225 – 280 millions years ago,the present day continent ware united in a single block called Pangea and sorrounded by ocean called Panthalassa .
The Pangea was located near the south pole.
Later Pangea split into two super continent ie Gondwanaland (South pole) and Laurasia(Along equator in northern hemisphere).The two super continent ware separated by narrow water body called Tethys sea
He assert that the Laurasia split to form North America , Asia , Europe and numerous land mass in Northern hemisphere such as Green land, Ice land and UK . &
Gondwanaland split to give present day South America, Africa, Australia, Antarctica, Indian sub-continent and other islands in southern hemisphere.”
This can be illustrated by digram below.

NOTE
Since a time continent have been drifting apart to occupy their present position , the drift is very slow about 2 cm/year (The drifting still progress ).
EVIDENCE TO SUPPORT WEGNER CONTINENTAL DRIFT THEORY.
-Structural evidence (Jigsaw fit):If continent ware brought together it will form one single land mass ie S.America , Sub-continent , Antarctica and Australia into Africa can fit to form single land mass . Also N.America fit in Europe and Asia.
-Geological evidence: Similar rocks in coastal margin of coastal continent Example:The rock of West Africa are similar interm of structure and formation to those of eastern coast of Brazil .
– Biological evidence:The study of fossil reveal that,the similar fossil of different time ware found in different place (ie similar animals and plants and other fossils are found in different continent).
-Paleo-magnetic evidence:This was done through Paleo-magnetic dating.When a rock heated and cooled they ware magnetized in same direction,but also show that rock from different part of the earth have shifted relative position magnetic field new path represent relative migration.
-Geomorphologic evidence:The different mountain in Africa and Europe show have same structure, formation Example . Structural formation of of fold mountain like Alps and Atlas mountain all are formed In Africa and one move nortword due to drift.
-Paleoclimatic evidence .
CRITIQUE OF CONTINTAL DRIFT THEORY.
-Alfred Wagner meddled in the field of geology: Haven’t enough knowledge to explain about geology as far he was dealing with meteorology.
– Misfit of some continent: Possibly not all continent fit exactly to each other if they could brought together.
-Wagner fail to explain the mechanism of drifting continent:The actual force which causes the drifting proces wasn’t explained clearly by Wagner.
– Wagner didn’t explain the development of glaciers in hot region of Australia.
IMPACT OF CONTINENTAL DRIFT
-Climatic change
-Land form formation like Rift valley,sea, ocean and mountain.
-Occurance of earth quake and Volcanic eruption.



2-PLATE TECTONIC THEORY.
This is the modern theory which come to explain the plate continental drift theory.
That term tectonic plate made up by two terms ie
Plate-the slab of solid rock
Tectonic- Greece word means to build
Therefore,
Plate tectonics is the theory that say earth lithosphere is made up by individuals plate that are broken down into over dozen large and small pieces of solid rock.
The piece of solid rock (plates) are large continental and oceansized plate, six or seven medium sized plates and several small ones.
Seven major plate are North America, South America, Eurasia, Africa,Indo-Australia, Pacific and Antarctica, as well there is many smaller pale (microplate) such as Juan De Fuca near Washington in USA.
The plate move relative to each other at rest of 5-10 cm/year and interact along the boundaries.
TYPES OF BOUNDARIES
i) Divergent boundary: This occur when two tectonic plates move away from each other.
In this boundaries there is high possibilities of occurrence of earth quake and Volcanic eruption.
The movement of this plate can produce feature like Rift eg Rift valley and oceanic ridges.
Example o of the boundaries are Mid-Atlantic ridge and Pacific ring of fire.
ii) Convergent boundaries:This occur when two plates come together.
In this boundaries the edge of the both plates buckle up into a mountain ranges or plates bend down into a deep sea floor trench.
The impact on this boundaries are destruction of oceanic crust , occurrence of a Chain of volcanoes, powerful earthquake and Trench like Mariana trench.
Examples of this boundaries are
iii)Transform boundary: In this boundaries two plates slide each other. The impact of this boundaries are
Example of this boundarie is San Andreas zone in USA which extended under water.
The digram below show types of boundaries.

CAUSE OF PLATE TECTONIC MOVEMENT..
1) Convectional curent: Convectional movement of magma in the mantl cause , some of magma to move laterally below lithosphere , the lateral movement drag the lithosphere leading the plate tectonics movement
2) Upwelling of magma:In the lines of weaknes like Mid-oceanic ridge the magma rush out cause the movement of plate.
3) Isostatic movement: This slight movement of plate when trying to create balance cauae plate movement.
4) Cooling and heating of the crustal rock.


EFFECT OF PLATE TECTONIC MOVEMENT
Effect/Impact of Plate tectonics is just like continental drift ie
-Formtion of Rift like Rift valley caused by weak divergent movement of plate.
-Formtion of mountain
-Formtion of trench like Mariana trench in Pacific
-Occurance of earthquake and Volcanic activities.

.