continental drift

• what is the continental drift theory? position of continents have changed through time
• who was the first to realise that continents fit together at one point? abraham ortelius
• who was the continental drift theory developed by? alfred wegner
• what has occurred since the split on the coastlines? erosion and deposition
• sea level changes are constantly changing the present coastlines
• how has the use of fossils supported wegner’s theory? (2) give examples of the 2 variables. (2) the existence of same species of land animals and plants on either sides of the atlantic. - species: mesosaurus and glossopteris
• suggest explanations for the presence of fossils in different continents before continental drift theory was accepted (3) 1. the pair of animals must have swum the ocean. 2. fertilised eggs of animals may have been carried by ocean currents. 3. animals may have island hopped on islands
• fossils of fresh water animals such as the mesosaurus can be found in 270Ma old rocks in two separate continents. explain how this can be used as evidence for the continental drift theory (2) 1. the same species cannot evolve separately 2. fresh water reptiles cannot swim that distance in salt water aka the ocean
• give reasons why using the modern coastlines does not give a perfect “jigsaw” fit. (2) 1. deposition - leads to overlap 2. sea levels are constantly changing the coastlines 3. erosion - leads to gaps in the fit
• what are striations? scratches found within the rocks formed beneath glaciers
• explain and give examples of evidence for continental drift: mountain chains and rock types same precambrian fold mountain chains found in both sides of the atlantic
• explain how ther continental shield areas have been used for evidence for continental drift and give 2 reasons for your answer. (2) in both continents 1. rock types match up. 2. shield areas same age
• explain how the shape of fold mountains can be used as evidence for continental drift. (2) 1. folds + faults follow the same trend 2. continuous belt across both continents
• use examples to explain how paleo environments have been used to reconstruct historical plate movement (4) 1. uniformatarianism - e.g coal deposited in equatorial conditions and latitudes. 2. evaporites can indicate: tropical latitude dry zones: -> where desert stones are produced 4. fossils (glossopteris) can indicate the environment
• using examples, explain how fossils helped to prove the continental drift theory (2) -fossils like the land based mesosaurus have been found in both continents. - this animal cannot swim, the continents must have been joined
• explain how striations have formed underneath glaciers (2) -striations are scratches in bedrock. - they are formed from hard minerals at the base of glaciers by scratching the bedrock below as the glacier moves.
• describe the characteristics of boulder clays (2) -a poorly sorted, coarse grained, angular sedimentary rock
• how are boulder clays formed and used for continental drift evidence? -form under specific glacial conditions evidence, uniformstarianism: - the reserve of boulder clay in africa means it used to be situated more near poles in the past
• name two rock types used as evidence for continental drift -coal. -red sandstone