What has caused most of the natural plant life in the american midwest to vanish?

The diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?

How do oceanographers measure the salinity of ocean water?

[fw.02]sinkholes are often formed as a result of the actions of. a.heat on recharge b.pressure on aquifers c.acid in groundwater d.minerals in hot springs