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Earth and Planetary Science is an interesting topic in its own right. At a time when we are increasingly concerned about the future of the planet and the impact of human activities on it, having so little in the way of dedicated earth science education is scandalous.
However, interestingly, this has led to a slight help for people studying triple science at GCSE. Earth science features as component parts of all the chemistry AND physics modules. Which is one of the few crossovers between the syllabi. Plate tectonics? Chemistry and Physics. So well worth knowing these basic facts:
* Alfred Wegner proposed the idea of Continental Drift in the early 20th Century.
* Other scientists disagreed with his ideas because:
a) he wasn't one of them - he was an astronomy graduate turned meteorologist.
b) they could not physically reconcile the strength of the oceanic crust and the momentum (what is momentum?) necessary for a continent to push it aside.
* In the 1950s oceanic surveying revealed:
a) mid ocean ridges
b) Magnetic strips on the sea floor, which were symmetrical across the ridges.
*Seafloor spreading involves hot material rising in ocean centres (causing ridges) before moving aside (causing symmetry either side of the ridge).
*This showed that the continents moved like rafts on the plates - not by ploughing through the crust.
*The energy for this process come from radioactive decay of elements (U, Th, K) in the Mantle. Which causes the mantle to heat up and convect.
Evolution of the Earth's Atmosphere is covered in Chemistry. You should know:
* CO2 is a molecule with 1 carbon and 2 oxygens.
* CO2 comes from volcanoes.
* CO2 is used by plants in photosynthesis
* CO2 is a greenhouse gas.
* CO2 Causes ocean acidification (Carbonic acid in seawater)
* Plants absorb CO2.
* Before plants the earths atmosphere had a lot of CO2 in it, and was very reducing (learn reduction and oxidation).
* Plants release O2 when they photosynthesize.
* Plants and photosynthesising micro-organisms changed the atmospheric balance. It is now 78% nitrogen and 21% oxygen and 1% everything else (including CO2). Where do you think the CO2 went?
* The increase in oxygen helped the Ozone layer to develop.
* The Ozone layer prevents some UV radiation reaching earth - and permitted further evolution of complex life.
* Human activities - the use of CFCs (Chloroflourocarbons) damaged the layer in mid 20th century. They are now banned, and the layer is still 50 years from full recovery.
Print this. Learn it. The questions will definitely come up - and when they do, this is all you need to know! Often the Plate tectonics questions carry a lot of points. This is because in the absence of a compulsory Earth Science GCSE the exam boards have had to address the subject in their Physics and Chemistry, and provide evidence that it will come up. Paper styles may change year to year - but these questions will appear every time!