continental drift and sea floor spreading Flashcards
Name the 5 pieces of evidence for continental drift
jigsaw fit, fossils, mountain chains, rock types, glaciation
How can you obtain the best jigsaw fit?
By using the 1000m depth contour
Why is there not an exact jigsaw fit?
Deposition and erosion have changed the coastline
What must be the same to prove that two rocks were once part of the same outcrop?
characteristics of mineral composition and physical features
Age determined by radiometric dating
What was the name for the northern supercontinent?
Laurasia
What was the name for the southern supercontinent?
Gondwanaland
How are fossils evidence for continental drift?
If the continents were always separated they wouldn’t have the same fossil records. However during the carboniferous period, land based reptiles( mesosaurus) and plants (glossopteris) are found in Africa and south America.
how is glaciation used as evidence?
Glacial striations and sedimentary deposits of angular poorly sorted and scratched pebbles in a fine grained matrix
What rocks can be used as palaeoclimatic evidence?
coal deposits only form near the equator, coral reefs only form in the tropics, red dessert sandstone form in hot dry tropical latitudes
How are magnetic stripes evidence for sea floor spreading?
Magnetic stripes are caused by the alignment of magnetic particles within the molten magma. These line up with the earth’s magnetic field and become frozen in position as the magma cools and solidifies. The earth’s magnetic field reverses every few million years and this causes the development of areas of normal and reversed magnetism.
how are polar wondering curves constructed?
a large number of rocks are collected and dated and the direction of palaeomagnetism measured and plotted
how do polar wondering curves provide evidence for movement of the continents?
curves the same= continents joined
curves diverge= continents have separated
