2007-10-13 11:55:03 · 13 answers · asked by jonathan beechwood 2 in Science & Mathematics ➔ Earth Sciences & Geology
The difference is the degree of undercooling. Flows of lava
are quenched on the outside often to glass, but at the surface
heat is being lost very rapidly and there is no time for crystals to grow, so with the loss of heat molecules and components \
assemble around a lot of crystalllization centers or nuclei.
Deepseated intrusions of magma have pressure and less undercooling (Tmelt- Tcountry rock) and less loss of heat. So
a few nuclei are able to orchestrate and choreograph the
molecules and components to crystallize more slowly and grow larger crystals and coarser grain, and dissolve back into the melt any excessive amounts of nuclei.
2007-10-13 12:10:10 · answer #1 · answered by Anonymous · 4⤊ 1⤋
Fine Grained Igneous Rock
2016-10-05 07:08:54 · answer #2 · answered by ? 4 · 0⤊ 0⤋
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What is the difference between fine-grained igneous rock and course-grained igneous rock?
2015-08-06 09:23:44 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Fine grained igneous rock- cooled really fast, so the crystals don't get much of a chance to get big and visible to the human eye.
Course grained igneous rock- Formed under earths surface so it takes a lot longer to form. This gives the crystals time to grow larger and more course.
It all really has to do with the speed in which the lava/magma cools.
2007-10-13 13:39:54 · answer #4 · answered by ♥ Pompey and The Red Devils! 5 · 4⤊ 0⤋
Simply put: A fine-grained (extrusive) igneous rock cooled rapidly. A coarse-grained (intrusive) igneous rock cooled slowly.
2007-10-13 12:12:03 · answer #5 · answered by Lady Geologist 7 · 3⤊ 0⤋
By example, obsidian is igneous and is glass-like. No discernible grain at all. Granite is very coarse grained, with crystals of the component minerals clearly visible.
2007-10-13 11:59:26 · answer #6 · answered by ZORCH 6 · 1⤊ 0⤋
Fine-grained rock: (eg basalt, rhyolite, andesite) cooled quickly (i.e. it was erupted out at the surface) so consists predominantly of very small crystal grains, most which cannot be seen individually without the aid of a microscope
Coarse-grained rock: (eg granite, gabbro, diorite...) cooled slowly giving the crystal grains lots of time to grow, (like in a magma chamber, underground where it's way hotter than at the surface) - hence large crystals visible to the naked-eye.
2007-10-13 12:34:07 · answer #7 · answered by Anonymous · 2⤊ 0⤋
You mean COARSE-grained, of course. In coarse-grained igneous rocks you can see the individual grains without magnification, in a fine-grained igneous rock you cannot.
2007-10-13 12:02:22 · answer #8 · answered by pegminer 7 · 1⤊ 0⤋
the degree of cooling determines the grain size. igneous rocks that have cooled quickly have very small grains...some you canot even see such as obsidian.
those that have cooled slowly have large grains like granite
the same holds true for crystal formation
2007-10-14 04:13:11 · answer #9 · answered by zioncanyon 3 · 1⤊ 0⤋
a course grained rock like granite forms when magma cools slowly thus allowing more time for crystal growth. Fine grained rocks like obsidian were from lava(magma erupted onto the surface) that cooled quickly not allowing time for crystal growth.
2007-10-13 16:58:33 · answer #10 · answered by 22 4 · 1⤊ 0⤋