ESCI 1101 Mod 2

Why can a stone arch be twice as wide as a stone lintel (two columns supporting a horizontal stone) if both are built of the same material?

In a lintel, the bottom of the horizontal stone is under tension and rock is weaker under tension than under compression. CorrectThis is the correct answer. Since the bottom of the horizontal stone is under tension, the stone can break easily. In an arch all of the stones compress on one another, so the stones are primarily under compression and rock can handle a lot of compressive stress before breaking.

All of the following statements concerning intra-plate earthquakes (earthquakes that occur in a plate's center) is FALSE?

Intra-plate earthquakes tend to affect relatively small areas, compared to similar sized earthquakes along plate boundaries. CorrectThis is the correct answer as it is a false statement. The basement rock in intraplate areas is cool and unbroken, so intraplate earthquakes can affect much larger areas than similar-sized earthquakes along active plate boundaries do. If you add in that buildings in intraplate areas are seldom constructed to be earthquake-resistant, you have the potential for a real disaster. The difference in area is due to the fact that basement rock along active plate boundaries tends to be warmer and is usually broken up into discrete blocks. Earthquake energy is not as effectively transferred across those blocks' boundaries, so earthquakes along active plate boundaries typically affect more limited areas.

What changes, if any, will occur as seismic waves pass from the Earth's lower mantle UP into the OVERLYING layer?

P-waves and S-waves could both slow down as they entered the overlying layer since it was even less rigid than the lower mantle. CorrectThis is the correct answer as the layer above the lower mantle is the asthenosphere, which is a heat-softened solid that is less rigid than the underlying lower mantle. So as P-waves and S-waves enter this less rigid solid layer both would slow down.

Which of the following statements concerning the 1755 Lisbon earthquake and its aftermath is FALSE?

The earthquake led to a growth in scientific knowledge that gave rise to a new 'Age of Optimism' in Western Europe. CorrectThis is the correct answer because it is a false statement. The Lisbon earthquake did not lead to the 'Age of Optimism' but ended it. 'Optimism' suggested that our present world was the best of all possible worlds and that if something was bad about it, the alternatives would have been worse and everything that occurred happened for a reason, according to a divine plan. However, the Lisbon earthquake, aided by Voltaire and others, shattered that philosophy. People could not understand why God would punish Lisbon and yet leave less religious cities untouched, so they began to realize that earthquakes were not divine retribution, but due to natural causes. Which proved to be the death knell for the 'Age of Optimism'

side view

normal or reverse fault

Map view

right or left lateral fault