Katelin Fallon
Earth Surface Processes – Exercise 1
Q1
Figure A
The driving force in this geomorphologic evolution is the sudden impulse uplift source of the soil, this is usually cause by a sudden plate tectonic shift under the soil.Because this driving force took place, soil erosion occurs. This is because the soil is at such an angle that the force of gravity plus the high flow of soil creep (Kg = 0.4) is above the soil's holding threshold. This means that soil will flow downward, causing the height of the formation to decrease over time. At first the flow is dramatic, decreasing over 1/3 of its height in only one unit of time [(0.05, 0.2) to (0.029, 0.3) (h, t)]. But as the slope of the formation decreases over time, so does the ability of gravity acting upon the weight of the soil. This means that the slope decreases to almost no slope as the figuremoves away from threshold for erosion. 3/3
Q2
Figure A
Figure B
Because Kg= 0.1 Figure B has a low soil creep, compared to Figure A, allowing for a larger impulse uplift source (Soil creep does not affect the uplift process. Instead, two processes occurred simultaneously at the time.) of (0.1, 0) to (0.2, 0.072) [(t, h)], and a slower erosion/creep process of the region when compared with a soil creep of Kg = 0.4 (Figure A). When (Kg = 0.4), the impulse uplift source is (0.1, 0) to (0.2, 0.052), this means it has a smaller uplift height; the difference is around 0.02 in height. High soil erosion/creep values cause the height of the impulse uplift source to be smaller (again, no relationship with uplift source. Just a peak height). Also becauseFigure A has a larger soil creep, more soil becomes eroded over time, meaning it has a steeper slope then the Figure B. The difference in soil erosion is:
Figure A (Kg = 0.4): (0.2, 0.052) to (1.0, 0). Figure B (Kg = 0.4): (0.2, 0.072) to (1.0, 0.02).
Figure C on the next page also shows the difference in soil lost through erosion, in a comparison graph of (Kg = 0.4) and (Kg = 0.1). Figure D is also important because it shows that when time = 0.5, meaning half of the time of the graph has pasted, (Kg = 0.4) has a lower soil angle and less soil then (Kg = 0.1). It further proves that with a higher soil creep (Kg) plus a downward gravitational force, height of an area will decrease quicker over time. 2.5/3
X-axis is Time (t), y-axis is Height (h), Green is (Kg = 0.1) and Blue is (Kg = 0.4)
Figure C
X-axis is length (x), y-axis is Height (h), Time (t) is 0.5, Green is (Kg = 0.1) and Blue is (Kg = 0.4)
Figure D
Q3 You just rotate the graph. What I need to extract the temporal profile directly from the h array. I want to know if students understand the 2-D matrix structure. Why don‘t you generate the profile with commands you used in Q2? 2/3
Figure E
Figure F
Q4. The major difference between Figure E and F are their uplift sources(their driving forces). In Figure E, there is only an impulse uplift source occurring between the time intervals of 0.1 to 0.2. After this, there is no longer force pushing the soil forcing upward. This means that the soil creep (Kg = 0.3) plus gravity (The fundamental driving force for soil creep is gravity. So, “soil creep and gravity” is not a good expression), are theonly forces acting upon the height and slope of the soil. Because Kg is soil erosion/creep (Kg itself is not soil creep. Just a coefficient), this means that the height of the figure is going to decrease over time as the soil is forced to erode to lower height levels. But in Figure F there is a step uplift source (a continuous uplift), which is constant over the entire time period shown in the figure. This means a tectonic force is constantly forcing the soil upward. You can see that the step uplift source acting on the height of the soil is greater then the soil creep (Kg =3) force. This means that even though some soil will erode over time, more soil will be pushed up, causing the figure to increase in height over time. The uplift slope gains soil height quickly from 0.1 to 0.5 (time), with a height increase of 0.14. But after this point the slope begins to slow as the soil creep and uplift curb one another’s forces. This means that eventually the soil will level off to a slope of 0 (reach to a steady state because the slope increases with height.), but at a large height. 3/3
11/12 = 9.6 Good.