January 16th 2012 Lecture
Formation f planet Earth 4500 million years before present ‘continental drift’ and
Pangea: 1912 (Alfred Wegener) sea floor spreading: 1960 (Harold Hess) Magnetic stripes
on the ocean floor and wander paths for continents: 1965 (Fred Vine) Mid-cean ridges
and hot spots: 1965 (tuzo Wilson) Plate tectonics and Wilson Cycle: 1967 (Tuzo Wilson)
4.5 billion years old – earths age
Continental drift – the larger plates in which the continents are embedded. Alot of
problem when Alfred made is theory. Continental drift is redundant. Its incorrect but
they don’t drift independently.
Magnetism use it to identify where rocks where, how old etc.
Re assembling Pangea (Wegener, 1912) -Alfred Wegener proposed that continents
moved by ploqinf rgeoufh rgw aw DLOOE. “Continental Drift”. This was rejected by most
geologists. Pangea consist of: Laurasia(northern part) (N. America and Asia) Gondwana
Pangea – all the lands
Laurensia (North America) Asian (Asia)
If you identify certain rock, it shows climate, climate belts, cold artic areas. Rocks tell
you something about the climate.
Making sense of paleobiology – south America – Africa, Africa-India-Antarctica, etc
G250 million year old glaciers – striations, modern glacier, the ore bodies these are the
commercial mineral deposit. We look for dispersed minerals.
1960s: The Ocean Floor Gets Mapped. New techniques and technology. Somethought
the ocean was flat. Geo-physical techniques – the ocean floors. Same techniques on
land. Generating sound and it is reflected back and the time it takes shows something.
Seismic reflection. Swath bathymetry accurate maps of the ocean floor.
Ocean floors are not flat. Mid-ocean bridge in the middle f the atlantic ocean. A feature
of all ocean. Middle of the ocean. Equal distance. then You see major factures. Then
western Pacific which are trenches. Deep water trenches of 9 km.
Harold Hess introduced idea of sea floor spreading (1962). Sea floor created at MOR’s
recycled into mantle at trenches* sea-floor spreading – new material coming in by
volcanoes. Subduction. Planet earth recycling.
Continuous Volcanic Activity Along mid-Ocean Ridges ‘smokers’ and mineral deposit. *
‘smokers’ super heated water is being released. Very hot water have a lot of metals and
when its cooled, the metals come out. Sulphides – copper, zinc.