# 2. Study the histogram, which should show a distinctly bi-modal…

2. Study the histogram, which should show a distinctly bi-modal distribution (i.e., 2 humps).
a) [5 pts] What kind of crust does each of the peaks or modes represent? Print out and then annotate the histogram with a pencil, indicating which parts of the histogram correspond to which kind of crust. Before proceeding with this, refresh your memory about isostasy, which explains the connection between crustal thickness, density, and elevation.
b) [5 pts] Why is one hump broad and the other narrow? Your answer should consider how the crust is created and/or modified by a range of geologic processes.
3. a) What is the average horizontal spatial resolution (in km) of our map at the equator? In other words, how much area do the pixels represent (you can think of a pixel as one square in this grid)? Look in the Workspace window, where you can see the number of rows and columns in ZI, our elevation grid that is used to make the map. It helps to know the latitude and longitude ranges of the data — you can see the minimum and maximum values in the Workspace. Give the spatial dimensions of each pixel at the equator in units of km NS and km EW. It helps to know that 1° of latitude is about 111 km (the equatorial circumference is 40,000 km; the circumference at the poles is 0).
b) are all of these pixels of the map have the same area in terms of km2? If not, why is this the case?