BIBLIOGRAPHY

ScienceDaily (2010) Plants From Ancient Gondwanaland Spread By Continental Drift And Transoceanic Dispersal [http://www.sciencedaily.com/releases/2007/08/070808101526.htm]

Heffernan, David Earth and Environmental Science. Marrickville NSW: Science Press (2009)

Col, Jeananda (2010) CONTINENTAL DRIFT [http://www.enchantedlearning.com/subjects/dinosaurs/glossary/Contdrift.shtml]

Cheong, Ng & Viren (2010) Fossil Distribution [http://library.thinkquest.org/17701/high/pangaea/pafoss.html]

Unknown. (2010) JUST DRIFTING AROUND [http://www.sjsd.k12.mo.us/curriculum/explorations/assessments/drifting.htm]

PDF/Adobe Acrobat. Continental Drift [http://www.sci.csuhayward.edu/~lstrayer/geol2101/2101_Ch19_03.pdf]

Direct Measurement

Advancements in technology now allow us to be able to directly measure and study the subtle movement of the earths tectonic plates through the use of laser measurement and satellite remote sensing the length between plate boundaries.

Because these plates can move in differet directions they are capable of colliding, separating and rubbing against surrounding plates. This can create a fault line in the middle of the plate, possibley resulting in a natural disaster occurance such an earth quake, volcanoe formation or tsunami.

These measurements serve as direct evidence of continental drift, proving that all the earths tectonic plates are constantly moving in different ways, which controls the movement of the continents on them.

Palaeoclimates

There are many types of rocks and minerals that can only be created when the climate is suited.

An example is the coal deposits found in Antarctica, which must be formed in a warm, swampy area. This leads us to infer that Antartctica was once a warm continent, which can mean that it was either once located in lower and warmer latitudes but due to continental drift moved to its current location in the South Pole, or that the poles were once warm and free of ice when these coal deposits form.

However, the second possibility has been ruled out by matching the age of the coal with that of glacial formations elsewhere. If the climate was cold enough to allow glaciers to form, the formation of coal would be impossible as the poles would be frozen.



This diagram shows the matching ancient climates on the continents when joined, emphasizing the link between each continent.

Because these continents once experienced climates that in the present day wouldnt be possible due to their location, we are only left to infer that they were once situated somewhere where it was possible, but has been moved through continental drift.

Fossil Distribution

Fossil distribution refers to the finding of similar fossils on separate continents in rocks that are roughly the same age, surrounded by layers that match each other, and are sometimes found no where else in the world.

This is stong evidence to support continental drift, because some fossils can only be formed under certain conditions that are no longer provided by the continent where they are found. This suggests that the continent was once in a more accomidating place, or joined to another continent so that it was possible for the organism to travel between them.

Examples of these are:

-Freshwater crocodiles found in Brazil and South Africa.

-Glossopteris, a fernlike plant that has been found in small areas in Africa, South America, Australia, India, and Antarctica

-Mesosaurus and Lystrosaurus. Both are reptiles found in places now separated by oceans

This diagram shows the mapping out of some fossils that are found on certain continents, where in present day would be separated by ocean, making travelling in between possible only if they were joined.

This evidence is effective in proving continental drift, because it was impossible for these past organisms to travel between continents over the ocean, so the only option is that they were once joined and are now separated through continental drift.

Age of Ocean Rocks and Sediments

Radioisotope dating has helped geologists prove that if a new crust is continuesly formed at oceanic ridges and is pulled apart sideways, rocks will get progressively older the further apart they are from the ridge.

The ocean basins formed at these ridges are relitively young compared to continental crust, being only 200 million years old. When the ages of the sea floor rocks are mapped, the pattern of sea floor spreading becomes aparent, with the newest oceanic crust being at the oceanic ridge while the oldest is the furthest from it.

The pattern of sedimentation on the sea floor near these ridges supports this direct dating. In comparison to the thickness of the sedimentation layers furthest away from the ridge, little or no sediment covers the rocks at the ridge, proving that ocean rocks increase with age the further they move away from the oceanic ridge.



This diagram shows us an oceanic ridge with the differently shaded rock layers signifiying the theory that the further apart the top layer drifs the older it gets, with the least oldest being in the middle.

This evidence convinces us to believe the continental drift theory, because we can see that new rocks are continuesly being formed at the oceanic ridge and the oldest rocks are going to consistantly separate, proving that they were once joined and are still in the process of separating.

Glacial Deposits

Glacial deposits are the result of ice and glaciers spreading over large regions outwards from the poles and scratching smooth rock and depositing unsorted sediments that can be identified and dated. About 300 million years ago the Palaeozoic glaciation left its mark on rocks now found on several continents that are as far away from the poles as the equator.

These features only fall into place perfectly when the continents are alligned in the jig-saw style and moved near the south pole, as demonstrated in the following diagram.



The widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift.



Advancements in technology have allowed scientists to study these glacial deposits, working together with the knowledge of past climates to give us a mapping out of glacial sediments created towards the south pole, on continents that are now found on the equator. This evidence compells us to believe that these continents were once joined near the south pole, with the effects of continental drift moving them apart towards the equator.

Cross-continental Geological Formations

The discovery of continental shapes served not only as worthy evidence for the theory of continental drift, but also encouraged geologists to further study the geological formations of continents that were believed to be once joined and compared them.

For instance when Wegener fitted South America and Africa together along their continental shelves, he found that large blocks of ancient rock formed patterns continuously across the dividing line, resulting in:

-The mountains that run from east to west across South Africa link with the range near Buenos Aires in Argentina

-The distinctive rock strata of the Karoo system in South Africa consisting of sandstone, shale and clay laced with seams of coal, were identical to those of the Santa Catarina system in Brazil.

With these continents joined and geological features mapped out, they acted as the pictures on jig-saw pieces.



This diagram highlights major rock formations in Africa and South America and shows how they can act as 'pictures on jig-saw pieces' once joined together

 These formations, together with continental shapes, proves as impecible evidence in support of continental drift, giving us no other option than to believe that the continents were once joined.