Homework 5- Chpt 11
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School
College of Southern Maryland *
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Course
1010L
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
2
Uploaded by ChefNeutron19676
Instructions
Part 1
1.
How does elastic rebound theory help to explain how earthquakes happen?
When under stress, rocks will flex elastically until the point is reached where the rock's strength
is exceeded by the elastic energy in it. At that moment, an earthquake occurs because of the rock
breaking.
2.
Explain the difference between magnitude and intensity as expressions of the size of an
earthquake.
An earthquake's magnitude is the quantity of energy it releases. Every earthquake has a single
magnitude, despite various methods for measuring it, and the results may vary greatly. The
degree of harm caused, or the emotions experienced is measured by intensity. The distance to the
epicenter and the kind of rock or sediment that underlies a region affect intensity.
3.
What type of earthquake is likely to lead to a tsunami? Why?
Large subduction earthquakes greater than M7.5 are likely to lead to a tsunami because they
cause the sea bottom to shift vertically.
Part 2
When we think of gold mining in the United States, most people immediately think of the
California or Alaska gold rusts. But did you know that concentrations of gold are associated with
metamorphic rock structures and that makes it one likely place to find gold right here in
Maryland? While Maryland has not sustained any long-term commercial gold supplies, hunting
for gold is still a popular hobby here in Maryland.
Let's start with a look at the Maryland Geological Surveys website:
http://www.mgs.md.gov/geology/minerals_energy_resources/gold.html
1.
Where in Maryland were most of the gold mines found? What geological region are they
all in?
Most of the gold mines in Maryland were found along the banks of the Potomac all past the
Great Falls, in a stretch of land about 10 miles. Gold is found in the Piedmont Plateau geological
region.
2.
Describe the details of the first discovery of gold in Maryland.
A private during the Civil war was stationed near Great Falls and while washing skillets in a
stream near McCleary’s hilltop he discovered the gold.
3.
When was the peak of commercial mining for gold in Maryland? When did commercial
mining end in Maryland?
The peak of commercial mining in Maryland was sometime before World War 2 between 1935
and 1940. Commercial gold mining ended in the 1940s in Maryland.
4.
What are some of the current regulations about gold hunting in Maryland today?
Current regulations include gold hunting must be done with the permission of the property owner
and collecting rocks is prohibited on state own land unless permission is obtained.
5.
Describe the process of panning for gold.
The process of panning includes getting a sample of gravel and swirling it around in the pan
underwater. Since gold is heavier it will sink to the bottom of the pan.
Today, if you wanted to find gold in Maryland, the best bet would be by panning along the rivers.
Rivers constantly erode their underlying rock surface which provides a continues (if small)
supply of gold.
Gold is commonly extracted from river till by panning.
Here are a couple of videos which show a hobbyist gold hunter working in Maryland. Not that in
the first video, he is also looking for old coins (which would be mined, processed, and then lost
to the environment gold samples) but it nicely shows the process of panning for gold. In the
second video he shows the process with a sample from Great Falls.
https://www.youtube.com/watch?v=rgWe46ZguNA
https://pubs.usgs.gov/circ/2004/1264/html/trip4/index.html
(Caution, this guy has a rabbit hole of videos. Looks like I am going to waste some time myself
watching)
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