Determination of Present-day Relative Motion in the Red Sea
Question
For this, we construct a spherical triangle (a triangle drawn on the surface of a sphere). The triangle has three vertices, at the Geographical North Pole (N), the Euler Pole (P) for the motion we are interested in, and at the point (X) for which we want to calculate that motion. Here is an example triangle:

All measurements in this triangle are made in degrees and each of the triangle’s sides is a great circle. The vector, v, is the velocity at point X.
Question:
Calculate the present-day relative motions at 20°N, 38°E and 27°N, 34°E in the Red Sea. Use the Arabia-Africa rotation pole (24.1°N, 24.0°E, = 4.2x10-7 degrees/yr).
Summary
This question belongs to geophysics and discusses about construction of spherical triangle and to determine the present-day relative motions in the Red Sea.
Total word count: 118
