He wanted to use humor to appeal to his audience
Earthquake mainly occur when there is rock movement along a crack on the crust of the earth. The slippage of the rocks causes shock waves that travel on the earth. A focus is a point on the earth where the actual movement takes place and an epicenter is a point which is directly above the focus. Seismographs are devices that record the earthquakes and do so by showing major waves patterns that is p-waves, s-waves and L-waves. Wave travel time from the epicenter to the seismic station can be estimated fro the travel charts.
In this case if the epicenter is 3200 km from the seismic station then the s-wave will take 11 mins 10 sec.
If we have a dark colored, coarse soil and reddish smooth soil for comparison, we can find lots of differences in them.
- The dark soil will have bigger layer of humus, while the reddish one will have a very small almost unnoticeable layer of humus.
- The color differs a lot, while the dark soil will have a dark brownish color, the reddish one will have intense orange-red color.
- The vertical profile of the soils will differ a lot; the dark one will have much bigger top two layers, while the reddish one will have very small upper layers and dominant middle layer.
- The dark soil will be rich in biomass, while the reddish one will be rich in iron and clay.
Answer:
7 - (-5) = 12
Hope this helps! Good luck :)