Why is it better for astronomers to measure parallax by observing every six months instead of observing every year

Sandstones that form in aeolian (wind/desert) environments appear very different from other sandstones, such as those formed in a beach/ shoreline environment and in rivers on land. give three identifying properties for each of the three sandstones that would tell a geologist which depositional environment they formed in. consider things such as the relationship between transportation and grain size, shape, roundness, sorting, fossils and composition.

According to the earth science reference tables, during which geologic time period were the continents of north america,south america, and africa closest together?

Alow-pressure belt means the air is cold and dry warm and rising cold and sinking warm and moist