Please answer the questions in just 3-5 sentences. 1) Describe at least three of
ID: 236134 • Letter: P
Question
Please answer the questions in just 3-5 sentences.
1) Describe at least three of the processes that may act on sediments as they travel to depositional environments.
2) Describe the differences between well-rounded and angular grains. What does rounding say about how far the grain has traveled? Why do sedimentary deposits tend to become smaller-grained and better sorted with greater distance from their source? Provide examples.
3) Describe metamorphic rocks. What types of rocks can be metamorphic? What happens to minerals within these rocks during metamorphism?
4) How are normal faults and reverse faults defined? How does the fault movement of normal faults differ from the movement of reverse faults?
5) Describe the characteristics of the simplest types of folds and the type of deformation needed to form them
6) What makes plate boundaries among the most dangerous places on Earth?
Explanation / Answer
1.
A) Smoothening of the sediment grains and reduction in grain size occurs from the friction amongst the sediment grains as they drift along with the river.
B) Sorting of the sediments occurs as they move along a river as the force required to mobilize smaller sediments is much less compared to the force required to move pebbles or other bigger sediment chunks. Hence, smaller sedimentary particles travel farther and sort along the river channel.
C) Cementing of the sediments can occur, when the matrix holding the sediments consolidates and solidifies, resulting in the formation of conglomerates or breccia.
2. The main difference between well rounded grains and angular grains is that the angular grains have freshly broken from their parent rock, whereas the rounded grains have been separated from their source long ago, and have been smoothened out by the friction between the sediments. The roundness of the sediment tells about the distance travelled by the grain as it underwent more tumbling or rolling and became smoother. Sediments tend to be sorted better from the distance because the smaller grains are easier to mobilize with lesser current in the river, hence the smaller grains are moving even when the flow is weak. This is the reason why beaches have the finest grains of sediments as they have been sorted by the sedimentation process.
3. Metamorphic rocks are often characterized by presence of foliation and lineation and some of them have thin to coarse banding present in their structure. Rocks like marble, gneiss, schist, amphibolite, etc can be metamorphic rocks. The minerals rearrange physically or thermodynamically within the rock depending upon the grade of metamorphism.
4. A normal fault is the result of crustal extension, and is also called as an extension fault. The hanging wall moves downward relative to the footwall at a steep angle. Reverse fault, unlike normal fault, represents compressive shortening of the crust and the hanging wall moves upward relative to the footwall, at a relative dip of 45 degrees or more.
5. Simplest types of folds are
These folds are usually formed by deformations which are ductile in nature as the rocks are not experiencing fractures in between.
6. Plate boundaries are often marked by the presence of volcanoes and frequent earthquakes which makes them a very dangerous spot on earth. The plates constant rub against each other and the pressure released from those processes create earthquakes, and the magma escaping through those will lead to volcanism.