Difference Between Magma and Lava

One of the most powerful forces of nature is the raging volcano. Huge spouts of molten rock literally come pouring out of the Earth. This molten rock is responsible for shaping the nature of most of the Earth's landscape, both above and below water. We also know that this molten rock exists below the Earth's outer crust before it occasionally over flows onto the surface of the planet. Most of us call this molten stuff either "magma" or "lava". There is a very distinct difference between magma and lava. Many of us use the words interchangeably, however this is incorrect. To help aid you to use the proper terminology when discussing

The Practical Difference between Magma and Lava

The main difference between magma and lava, and the point that a geologist will bring up first when discussing the difference, is that strictly speaking magma exists underground. When magma erupts through the a volcano or a vent in the Earth, it immediately becomes lava.

The Compositional Difference Between Magma and Lava

There is also a compositional difference between magma and lava.

When magma does form rocks it usually does so very slowly because of the long amount of time it takes for the liquid to cool and solidify: it is much more difficult to dissipate heat underground than it is in the open air. Because of this extremely slow cooling process, magma tends to form rocks with a high concentration of crystalline substances. When these rocks reach the surface, through erosion or other geological disturbances, they are known as igneous rocks. The high crystalline concentration is the reason that many igneous rocks sparkle distinctively.

The compositional difference between magma and lava occurs because lava tends to cool much more quickly than magma does because lava only exists on the Earth's surface where heat can dissipate into the open air. Because lava cools so much more quickly than magma there is little time for crystals to form and thus rocks formed from lava tend to have a much lower crystalline density than rocks formed by magma.

The Etymological Difference between Magma and Lava

As we have seen the difference between magma and lava is not a particularly dramatic one. The last difference between magma and lava therefore is simply in the words we use for them.

The word magma comes from the Greek root "massein" which means "to knead" or "to mold." This is presumably because it's well known that magma forms many of the Earth's landforms.

The word lava comes from the Italian word, "lava", which means a torrent or steam. Etymologists usually presume this is due to the way lava will flow down a volcano in streams or rivulets during an eruption.