Teaching the Dynamic Earth Plate Tectonics Interactive Master sheets

Transcription

1 Teaching the Dynamic Earth Plate Tectonics Interactive Master sheets Contents Page Master Sheets for continental jigsaws Gondwanaland continents (blank outlines)...2 Four continents, showing gaps and overlap areas...3 Gondwanaland showing former ice cover...3 Africa and South America, with geology...4 Gondwanaland continents with fossil evidence...5 The evolution of a theory plate tectonics...6 With the support of: UK Offshore Operators Association (UKOOA) is the representative organisation for the UK Offshore Oil and Gas Industry. Its 35 members are companies licensed by the Government to explore for and produce oil and gas in UK waters. The Earth Science Education Unit. Copyright is waived for original material contained in this booklet if it is required for use within the laboratory or classroom. Copyright material contained herein from other publishers rests with them.

2 Fig 1: Gondwanaland continents (blank outlines) Best copied onto thin coloured card a different colour for each jigsaw i.e. 6 colours 2

3 Fig 2: 4 continents, showing gaps and overlap areas Source: Mainly O.U. S102 Plate Tectonics: a revolution in the Earth Fig 3: Gondwanaland showing former ice cover Source: Mainly O.U. S102 Plate Tectonics: a revolution in the Earth Sciences, Fig. 14 overlaps Areas covered by ice sheets million years ago (rather conjectural for Antarctica because of modern ice cover!) gaps Direction of movement of ancient ice sheets Notes for Fig 2: The fit of the Atlantic continents at the 500 fathom (approximately 1,000m) contour. Solid colour indicates overlaps; stipple indicates gaps. Some of the overlaps can be accounted for by features that have grown since the Atlantic opened (for example, the Niger Delta and the area off Florida). Note that Iceland is left out of the reconstruction for this reason; it is a pile of volcanic rock that has erupted since the Atlantic began to open. (See the TV programme Volcanic Iceland ) 3

4 Fig 4: Africa and South America, with geology Source: Mainly O.U. S102 Plate Tectonics: a revolution in the Earth Sciences, Fig Rocks deposited Ma ago (= millions of years ago) Very similar sequences Freshwater beds, passing upwards to salt deposits, then shallow marine beds. Rocks older than 2000 Ma (= millions of years ago) Rocks formed between 600 and 2000 Ma 4

5 Fig 5: Distribution of land/freshwater animals and plant in the continents of Gondwanaland Source: This Dynamic Earth, U.S.G.S. Cyn = Gloss = Lys = Meso = Fossil remains of Cynognathus, a Triassic land reptile approximately 3m long. Fossils of the fern Glossopteris, found in all of the southern continents, show that they were once joined. Fossil evidence of the Triassic land reptile Lystrosaurus. Fossil remains of the freshwater reptile Mesosaurus. 5

6 The evolution of a theory - plate tectonics 1912 Alfred Wegener His ideas were published in a book in English in 1924 called, The Origin of Continents and Oceans. His idea was called continental displacement which later became, continental drift. His book contained five major lines of evidence: a) the jigsaw fit - the very close match between the coastlines of Africa and South America; b) matching of the geological patterns from either side of the south Atlantic (the pattern on the jigsaw) c) fossil evidence (Mesosaurus - a reptile, Lystrosaurus - another reptile, Antarctic beech) d) palaeoclimatic reasoning e) He attempted to show the movement of continents by the change in their distance apart, shown by timing radio transmissions over a number of years. Wegener died in Jason Morgan, Dan McKenzie and Xavier le Pichon Developed all the earlier ideas into plate tectonic theory 1858 Antonio Snider Published first map showing Africa and South America joined together - they broke apart during Noah s flood J. Tuzo Wilson Proposed that the Earth is divided into several large rigid plates - these are moved apart as sea floors spread Alexander Du Toit Published, Our wandering continents. Compiled a lot of geological evidence supporting the continental drift idea (ie. matching rocks on either side of the Atlantic) F.B. Taylor He envisaged a mighty creeping movement of the Earth s crust and collision with other continents to explain the Tertiary mountain belts, e.g. the Himalayas and the Alps Francis Bacon Noticed that the coastlines of Africa and South America had similar shapes Fred Vine and Drummond Matthews Explained the symmetrical magnetic stripes on the ocean floor in terms of sea floor spreading S.K. Runcorn et al Palaeomagnetic evidence from continental rocks appeared to show that the magnetic poles of the Earth had moved - polar wandering (it was later shown that not the poles but the continents had moved) Eduard Suess The rock structures on either side of the Atlantic were very similar - but this was explained by the collapse below sea level of a supposed continent in between Atlantis Harry Hess Proposed that new ocean floor was made in the centres of oceans and then carried sideways on convection current conveyor belts - this became called the sea floor spreading hypothesis Arthur Holmes Proposed that there were convection currents in the mantle below the crust. These events are in jumbled order. Cut them into strips and re-assemble to give the correct sequence. 6