PEO 2 Lecture Cards - Gravity and Magnetism Flashcards
What is the equation for gravity?
F = G ((m1 x m2)/d)
What is the equation for gravity?
F = G ((m1 x m2)/d)
What is the equation for gravity?
F = G ((m1 x m2)/d)
Define Isostacy.
Earth’s crust behaves as if it is floating on the underlying denser mantle, in much the same way that ice floats on water.
Define Isostacy.
Less dense blocks float higher. Denser blocks float lower.
Put these in order of thickest and less dense, thinner and denser, and even denser (Oceanic crust, mantle, continental crust).
Continental crust, oceanic crust, mantle.
There are two major consequences of accepting the Theory of Isostasy. What are they?
- Over the long term the substrate beneath the crust must behave as fluid (rheologic solid).
- Earth’s crust is not very strong over the long term, and segments behave as if they are not linked, so it can bend and equilibriate.
Mountain ranges have _____.
Roots
The Theory of Isostasy was proven true by documenting _____ crust in areas formerly covered by sheets of ice sheets or large lakes.
Rebound
Earth is a(n) _____. Compressed at poles, expanded at the equator.
Oblate spheroid.
Earth’s crust becomes _____ under a load, and _____ when the load is removed.
Depressed; rebounds
Bouguer Gravity Anomalies - For all continental landmasses the Bouguer anomaly is _____, and it is more _____ with greater elevation.
Negative; negative
Why do mountains have high elevations?
Mountains have high elevations because they are the tops of thick accumulations of low density crust that rides high because of isostasy.
Bouguer Gravity Anomalies - For all ocean basin locations the Bouguer anomaly is _____, and is more _____ with greater depth.
Positive; positive
The only “exceptions” to the rule are Bouguer anomlay values at _____; and where there are rock masses with unusually high (metallic ores) or low (hot rocks) densities.
Ocean trenches
What are the exceptions to the Bouguer anomaly rules?
- The Bouguer anomaly values at ocean trenches where rocks are mechanically warped downward. Trenches tend to have low positive anomalies (not in equilibrium).
- Where there are rock masses with unusually high densities (metallic ores) among rocks of lower density (continental crust).
- In volcanic areas such as island arcs (thermal inflation and rocks of intermediate density). Island arcs tend to have low positive to low negative anomalies.
Earth’s magnetic field is a _____, as if a bar magnet occurred in Earth.
Dipole
What is the degree of inclination at Earth’s North and South Poles?
90 degrees
What is the degree of inclination at Earth’s equator?
0 degrees
