Syracuse, NY
Fall 2011
Exam #2
Part I Short Answer, your answer should be a short sentence (5 pts each).
1. What is a point bar?
The inside curve of a meandering stream that has the lowest current velocities and has the least erosion.
2. What is lahar?
This is a hot mudflow associated with volcanic eruptions.
3. What is an oxbow (lake)?
Oxbow lakes are formed along meandering river systems when opposing cut-banks along a river meet up and create a meander cut-off, these meander cut-offs are then separated from the river channel by point bar deposits.
4. What is lave?
Lava is molten rock, found above or at the Earth’s
surface (where as magma is found below the Earth’s surface).
5. What is a flash flood?
This is a flood associated with steeper regions (mountain valley’s) characterized by high discharge for a short duration (short period of time).
6. What is recurrence interval?
The period between natural events (series of events), like between floods or volcanic eruptions.
7. What is soil creep?
The slow downhill movement of soil/rock (mass wasting) resulting from freeze-thaw behavior (freeze expansion and melt contraction).
8. What is a tropical cyclone (hurricane)?
An ocean based storm, with a circular wind patterns, with sustained winds of over 74 mph.
9. What is an ash fall?
These are eruptions of volcanic ash (from a volcano) into the atmosphere that then rains down over a large region around the volcano, and downwind from the volcano.
10. What is a sinkhole?
A circular depression at the surface created when a cave or underground cavity collapses, causing the surface to move downward.
Part II Diagram, fill out the diagram below (5 pts).
11. On the figure
below, note on this meandering stream where the cut bank and point
bar are located, and which side of the stream is erosional and which
is
depositional in the
spaces provided.
Part III Long Answer, your answer should be well written & be complete. (11 pts each).
12. How does water (precipitation) affect the mass wasting? Give two affects that water has, and describe how it increases or decreases the probability of a mass wasting incident occurring.
Water increases the probability of mass wasting. It does this by 1) increasing the weight of the soil, and thus the affect of gravity acting on the slope (i.e. increase the driving force downhill); and 2) decreasing the affect of friction within the soils and rock on the hillside, thereby reducing the resistance of the slope to movement.
13. What is viscosity, and how this affect volcano development and risk associated with volcanoes?
Viscosity is a fluids resistance to flow and magma viscosity is controlled by its chemistry (silica content) and its temperature. Volcanoes are strongly influence by magma viscosity, with more viscous magma resulting in the development of composite volcanoes and magma domes, and less viscous magma producing shield volcanoes and flood basalts. In addition, the more viscous a volcanoes magma the greater the likelihood that the volcano will have an explosive eruption. This difference in volcano shape, size and explosiveness is the result of magma viscosity and how the magma flows and releases gases contained within the magma.
Points that could be discussed here included; volcano slope, magma chemistry, magma temperature, gas content, and eruption style for various volcano types relating the viscosity of the magma.
1.
14.
What are some of the possible methods of forecasting volcanic
eruptions; what do they tell us regarding volcanic activity; and which were
utilized during the eruption of Mount Pinatubo?
Several of
the following methods of forecasting volcanic eruptions should be described:
1) Monitoring
gas emission from the volcano.
2) Monitoring
tilting and swelling of the volcano.
3) Monitoring
seismic activity of the volcano.
4) Monitoring
thermal, magnetic, and hydrologic conditions around the volcano.
5) Study the
geologic history of the volcano; including timing of eruptions, size of
eruptions, and types of material erupted in previous volcanic episodes
(indicating types of hazards associated w/ these eruptions).
During the 1991 eruption of Mt. Pinatubo gas emissions, seismicity and geologic history monitored and studied.
15. What is meant by flood plain regulation; define what flood plain regulation is and be able to describe the process of regulating development to reduce the impact of flooding? If a sketch of a river and its associated flood plain would be useful, one is provided below for your annotation in this answer.
This answer should center on how to reduce the risk of flooding, not by reducing flooding, but by planning development. Flood plain regulation is the process of mapping (or delineating) the location of flood plains (where flooding will occur and how often) and then using this information in regulating development in these areas. In your answer you need to discuss how mapping would occur and then discuss the two types of regulation covered in class, namely, zoning and building codes. Describe where each is appropriate and why.