matematika wrote: Unome wrote:
matematika wrote:When are gravity anomalies positive and when are they negative?
Consider the meaning of a gravity anomaly being positive or negative in the simplest sense. Now think of several different geologic features and determine whether their anomaly would be positive or negative. Make sure to account for corrections - typically, the most common interpretable anomaly is the Bouguer anomaly.
I know the meaning of a gravity anomaly, but how do I relate that to landforms? I know that negative gravity anomalies relate to thick crusts, but then why aren't mountain ranges negative gravity anomalies?
Gravity anomalies aren't so much affected by the thickness of crust as by the amount of mass (because, y'know, GMm/r^2 type of stuff). Yes, if you just add mass on top of an existing landform, making a thicker area of the same density, you should have more gravity, but that's not what happens with a mountain - isostasy means the mountain also has a deep extent into the mantle of less dense crustal material.
But honestly, I just spent a lot of time answering these questions based off a chart I found relating free air and bouger anomalies over different features, and kind of mindlessly copying, so idk.
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