Why lava cools down into a black solid?

Question

Anyone?

Answer 1

Lava is extremely hot rock in liquid form. It becomes red/orange in color because of its temperature change. If you've ever seen a piece of iron heated slowly, you'll notice that it changes in color many times. The same thing happens with lava/magma.

When it cools, it reverts back to its rock/mineral solid form. Basaltic lava is one type of lava (common to a shield volcano like the hawaiian islands). Basalt (a methamorphic rock) is grey to black in color due to its high pyroxene content. Pyroxene has a lot of aluminum or magnesium content, giving the cooled lava its dark color.

http://volcanoes.usgs.gov/Imgs/Jpg/Photoglossary/20011005-0039_DAS_large.jpg

This link (above) shows a picture of a partially heated piece of basalt.

Does this help?

Answer 2

It doesn't all cool down to a black solid. There are many different colors of obsidian, which is a volcanic glass that comes from lava flows.

Frozen lava is also not only black, but can be also red or grey. These are also called igneous rocks, and come from both lava flows and magma intrusions.

Answer 3

Most of the answers so far have not really answered the question, except for one. Lava doesn't always cool down to form a black rock. Only the more mafic lavas do. Mafic is a type of igneous rock with little silica (feldspars and quartz) present. Mafic rocks (and lavas) have more iron, magnesium, aluminum, manganese, etc. Felsic rocks and lavas have much more silica but not a lot of those other metals. Granite is a felsic rock, basalt is mafic. A very mafic lava will turn into black basalt (or gabbro) while a felsic lava will turn into gray or whitish andesite or rhyolite.

Answer 4

Lava is exposed at the Earth's surface (vs. magma), so it cools quickly and doesn't have time to differentiate (separate out) to different minerals like a granite (cooled from magma, under the surface). The result of the quick cooling of lava is an undifferentiated black solid rock.

Answer 5

because thats what color it is when the rock is cool.

if youve ever seen a blacksmith work on metal, when he starts he has some iron and its black, he heats it up and it glows red, and then after working on it and then cooling it with water, the color goes back to black. the glowing is from the heat, just like the center of the earth, and the rock will return to its original color when it cools down.

Answer 6

Because lava is superheated melted rock...so when it returns to its' solid state, it's rock.

Answer 7

its ash