Question

Question 1:What is the behavior of seismic waves as they pass through dense rock (mountains)?What about a medium of softer sediment (valleys)?During the amplification animation, what happens to the energy waves as they passthrough the valley and reach the mountain? What type of material do you expect to findin valleys (Hint: there is a river there, and yes there is some water but that is not it)?Explain the motion of crustal masses that is observed during a normal fault.What landscape evidence may be indicative of a normal fault?What similarities can you find between a thrust fault and a normal fault in terms oflandscape modification?

Answer 1

1. Seismic waves passing through dense rock (mountains) tend to travel faster and experience less amplitude (less shaking) compared to when they pass through a medium of softer sediment (valleys). When seismic waves pass through softer sediment, they tend to slow down and experience greater amplitude (more shaking). This is because the softer sediment has a lower density and stiffness, which allows seismic waves to travel more slowly and with greater amplitude.

2. During the amplification animation, as the energy waves pass through the valley and reach the mountain, the amplitude (or shaking) of the waves increases. This is because the softer sediment in the valley allows the seismic waves to slow down and amplify, and when the waves reach the denser rock of the mountain, they are reflected and refracted, causing the amplitude to increase even further.

3. In valleys, you would expect to find sedimentary rocks, such as sandstone, shale, or limestone. These rocks are formed from the accumulation of sediment (including sand, silt, and clay) that has been deposited by a river or other body of water.

4. During a normal fault, the crustal masses move in opposite directions, with one side moving downward relative to the other side. This motion is caused by tensional stress, which pulls the crustal masses apart. As the two sides move apart, a gap (or fault) forms in between, which can eventually become filled with sediment or volcanic material.

5. Evidence of a normal fault can include the presence of a fault scarp (a steep slope or cliff that forms along the fault line), a fault line (a visible break or crack in the ground), or offset features (such as a river or road that has been displaced by the fault motion).

6. Both thrust faults and normal faults can cause significant landscape modification. Thrust faults can cause large-scale folding and uplift of rock layers, which can create mountains or other elevated landforms. Normal faults can create rift valleys or grabens, which are depressed areas between two parallel faults. In both cases, the faulting can cause significant changes to the topography of the landscape.