... land inside the Earth. On the other hand, physical oceanography looks at the oceans and the rocks beneath them. Next, the passage describes historical geology, which mayinvolve the study of ... which means the writer gives first-hand information, or if the sourceis a secondary source, which means the writer givessecond-hand information. Another point to consideris whether the source ... and wheels and axles.Simple machines like these are useful becausethey can multiply the force applied to them andthey can change the direction of that force.Levers are used to lift and push....