please help me! :(
2007-03-12 11:05:00 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
When our earth was young, it was a fast rotating fire ball orbiting the sun. Over time, it cooled down until the surface started to solidify. First very thin and still hot until it reached today's thickness. However, earth's core is still hot with the elements in liquid or even gassy form. And the gravity of sun and moon plus centrifugal forces of its own motions are still pulling on the planet's shape, causing the continental plates to move. This frequently causes "valves"(volcanoes) to open in order to release the due pressure. Most volcanoes are located at or near those tectonic plate boundaries.
But the overall slow-down trend will cause a decrease in volcanic activity until its total halt in a few billion years, which will come along with the end of earth's rotation and all other related activities that our planet still shows us today.
2007-03-15 20:03:27 · answer #1 · answered by McMurdo 3 · 0⤊ 0⤋
Because the pressure from earth's molten core pushes it up to the surface.
2007-03-12 18:08:13 · answer #2 · answered by opium_4_life 2 · 0⤊ 1⤋
Hi. The crust floats on the magma, and the pressure can force molten material out. Magma. Don't you just love the sound of it. Magma?
2007-03-12 18:08:47 · answer #3 · answered by Cirric 7 · 0⤊ 1⤋
They get less dense because (as per boyle's law) when something gets warmer, it's volume increases, but its mass stays the same, so density gets less
2007-03-12 18:09:13 · answer #4 · answered by MLBfreek35 5 · 1⤊ 0⤋