Which would have larger crystals: an igneous rock formed from magma that cooled deep below the surface, or a igneous rock that cooled from lava on the surface? Explain why.
2006-12-06 04:17:36 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
When crystals cool slower, they grow bigger. Those that cool on the surface are smaller.
2006-12-06 04:20:59 · answer #1 · answered by science teacher 7 · 2⤊ 1⤋
Interestingly enough, while slowly cooled magmas have larger crystals, quickly cooled magmas have MORE crystals. I always thought that odd. So a piece of gabbro will have bigger crystals, but the basalt will have more. It has to do with the Gibb's Free Energy of Formation. Basically, when you cool something rapidly it takes less energy to form many smaller crystals than to remain in a melt and cool slowly.
2006-12-06 16:51:46 · answer #2 · answered by Cassie 1 · 0⤊ 1⤋
Slow cooling at depth allows big crystals to develop but its not the whole story. You also need the right ingredients present - if you don't have those you'll never get big crystals. Also you can grow big crystals quickly if you've got shed loads of the right elements present.
We used to melt batches of tonnes of a mineral at over 2000 deg C so all the light silicates floated to the top to form a crust. Left to cool for several days we got spectacularly large crystals growing both on the surface and in the melt itself.
2006-12-07 09:09:47 · answer #3 · answered by black sheep 2 · 0⤊ 1⤋
The larger crystal will probably be in the rock which cooled at more depth. Crystals take time to grow to be large, so they grow larger in magma which cools more slowly. Magma at depth is closer to its heat source and is more insulated by surrounding rock than magma nearer the surface, so it will cool more slowly and grow larger crystals.
2006-12-06 05:29:02 · answer #4 · answered by PoppaJ 5 · 0⤊ 1⤋
As magma cools slowly over thousands of years, deep in the earth, crystals have time to grow large and fall out of the magma (e.g. granite).
When magma is exposed to the open air it cools very fast and crystals don't have a chance to form (e.g. basalt).
2006-12-06 04:39:31 · answer #5 · answered by dtbrantner 4 · 1⤊ 1⤋
extremely tough situation. look into from bing and yahoo. just that can assist!
2014-11-01 17:28:24 · answer #6 · answered by Anonymous · 0⤊ 1⤋
quickly
2016-05-23 01:00:44 · answer #7 · answered by Anonymous · 0⤊ 1⤋