<jupyter_start><jupyter_text>> **Note**: This is a version of the practical without the code. I will use this during class and fill in the code live. I encourage students to type along with me since it can help with understanding and retention of the content. You will always have the full version as a reference. Gravity and the isostatic state of the lithosphere**Goal:** Determine the relationship between observations (gravity disturbances and topography) and the isostatic state of the lithosphere.The isostatic state of the lithosphere (under an Airy or Pratt model) is tied to its density structure. As such, we would expect observations of gravity disturbances to yield some knowlegde on isostasy since they are sensitive to variations in density. In this practical, we will work global observations of gravity and topography, determine a physical/mathematical relationship (a model) between these data and isostasy, test whether our model fits the observations, and reason about why is does or does not.   Import the required librariesLoad the required software to load the data, make maps, and perform calculations.<jupyter_code># For arrays and linear algebra
import numpy as np
# To load and manipulate grids
import xarray as xr
# To make figures and maps
import matplotlib.pyplot as plt
# To add cartographic projections to our maps
import cartopy.crs as ccrs<jupyter_output><empty_output>
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