L3
讲座
1. What is the lecture mainly about?
The process by which tecatonic plates are separated
The recent discovery of an unusual tectonic plate
The effects of underwater riffs on plate boundaries located on land
The development of a new technology for studying rifts located on land
2. Why does the professor mention Iceland?
To support the claim that rifts occur wherever volcanoes occur
To point out that Iceland is located on a plate boundary
To give an example of a rift area that is located on land
To give an example of an extraordinary active rift system
3. What unexpected discovery did scientists make while studying the rift event in East Africa?
Rifts can widen more quickly than previously thought.
Some magma deposits lie closer to Earth surface than geologists realized.
Volcanic activity is not necessary for rift formation.
Volcanic activity along land rifts is different from activity along underwater rifts.
4. In the lecture the professor discusses an event that occurred along a rift in East Afiica. Place the stages of this event in order.
Molten rock flowed into the rift and widened it.
There was a brief period of inactivity.
Seismic activity began 30 kilometers south of the northern volcanoes.
There was a series of earthquakes near the northern volcanoes.
5. According to the professor, what may eventually occur at the location of the recent rift event in East Africa?
Underground earthquakes will become more frequent.
Two tectonic plates will merge.
A deep basin will form.
A new fissure will open.
6. What does the professor imply when he says this:
The East Africa Rift System is much larger than previously thought.
East Africa Rift System’ is an obvious name fbr the system.,
Not all of the East Africa Rift System is located in Africa.
