Questions & Answers
The tides are a result of the difference between the forces of gravity on opposite sides of the Earth. Because the Earths diameter is such a small fraction of the Sun-Earth distance, the gravitational pull only changes by 0.017% across the Earth. But for the moon that difference is 6.8%, 400 times greater. If you factor in the overall stronger pull from the Sun this means that the Sun’s tidal effect is only 44% that of the Moon.
There is approximately 1,450 million billion tonnes of water in the worlds oceans. There are two main theroes about where it all came from.
1. On early Earth, hydrogen and oxygen molecules combined and emerged as steam from volcanic eruptions.
2. Ready made water molecules arrived from Earth from comets which would have being bombarding the early Earth.
Until recently the largest volcano in the solar system was thought to be Olympus Mons on Mars. However, recent research has revealed that the Tamu Massif, a submerged shield volcano 1,600km east of Japan is actually larger.
The Tamu Massif, which erupted between 130 and 145 million years ago, is about 640km wide and covers and area of about 190,000 square kilometres.
In comparison, Olympus MonsÂ is only 595km across, although it is thought to be 25% more massive overall.