Download 12.1 Earth Note answers

12.1 Notes Answers
What evidence did Wegener give to support the theory of plate tectonics?
Continents looked like they fit together
Fossils
Coal deposits
Glacier evidence
Mountains, rock formations
What was the name of the supercontinent? The supercontinent was named
Pangaea
What evidence did Wegener find regarding geologic structures and rocks to
support his theory on continental drift?
1. mountain ranges that begin on one continent, end at the coastline and appear
to continue on a continent across the ocean
2. rock structures were similar
3. the ages of rocks in newfoundland and Greenland and Ireland and Scotland
and Norway were similar
What was Mesosaurus
small freshwater reptile that was sharp-toothed
Why was it important to the theory on continental drift?
Because it was small, freshwater animal, unlikely to have survived 6000km crossing
of open ocean
What other fossils did Wegener study?
Cygnathus and Lystrosaurus on the southern hemisphere continents
Glossopteris was a fern found widely apart. It did not grow in cold climates
(Therefore Antarctica must have been closer to the equator and warmer)
Why were scientists studying paleoglaciation puzzled by evidence of glaciers
in Africa and India?
They found evidence of glaciers in regions that are now tropical (India, Africa)!!
What was another piece of climate evidence that reveals that the continents
were not always in their current positions?
Coal deposits in Antarctica (tropical swamp material). Therefore Antarctica was
once in a warmer location than it is now.
How did mapping the locations of volcanoes and earthquakes help to support
the continental drift theory?
Volcanoes and earthquake zones outline the boundaries between tectonic plates
What is a tectonic plate?
Large, movable slabs of rock
What is the mid-Atlantic Ridge?
A long mountain range running North-South down the length of the Atlantic ocean
(middle of the ocean floor)
What was discovered about the age of the rocks found near the Mid-Atlantic
Ridge?
The youngest rocks were found closest to the ridge and older ones were further
away.
How did the thickness of sediments change the further away from the ridge
scientists studied?
The layer of ocean sediment (silt/organic debris) was thicker further away from the
ridge
What is magnetic reversal?
Earth has a North and south magnetic poles and magnetic field. Ancient rocks
preserve the Earth’ s magnetic field as it was when the rocks were formed. Magnetic
reversal is seen when the direction of the magnetic field of the earth completely
reverses (about 4-5 times per million years and may be due to the movement of the
liquid iron)
How does magnetic striping, discovered during the early studies of
paleomagnetism, help to support the continental drift theory? What is the
name of the process that occurs at the mid-Atlantic Ridge, and which helps to
explain the theory of continental drift?
Magnetic striping shows the pattern of stripes in the direction that the ironcontaining materials (Basalt) pointed on the earth’s floor over millions of years. The
same pattern was seen the same on both sides of the ridge and alternated. Magma
cooled with a given direction, then was pushed aside as new magma emerged and
laid down an opposite magnetic orientation of the basalt.
What were the nine pieces of evidence Hess presented to support the idea of
sea floor spreading?
See Table 12.1 on p 513
What is a hotspot?
Area where molten rock rises to earth’s surface (eg. Hawaiian islands)
What is the name of the unifying theory of geology? Plate tectonic theory