L Latitude: angular distance north or south from the earth's equator measured through 90 degrees. Lithosphere: solid, rocky, outer part of the Earth, approximately 50 miles thick, comprised of the crust and the solid portion of the mantle.  Longitude: the arc or portion of the earth's equator intersected between the meridian of a given place and the prime meridian and expressed either in degrees or in time. Love Waves: surface waves that move parallel to the Earth's surface and perpendicular to the direction of wave propagation..