Anna Wilkinson, age 13, of Denton, Texas, for her question:
WHAT IS IN LAVA?
Lava is the molten rock that comes out of volcanoes when they erupt. The lava cones from deep within the earth where the heat is great. The hot material is a solution of silicate and is similar to the liquid that would result if granite or basalt were melted.
When lava cools quite rapidly, only a few crystals can form. The lava then hardens into a rock that contains large amounts of natural glass.
When lava first comes out of a volcano or from a crack in the earth, it is red hat and reaches temperatures from seven to 10 times hotter than boiling water.
Volcanoes that contain lava are sometimes explosive. From time to time they blow out large amounts of dust and rock fragments that form layers between lava flows.
Some types of lava contain large amounts of dissolved gases. As the gases expand, they are trapped in the lava and form many bubbles. Pumice is a type of lava that contains many bubbles.
Lands that were once covered with lava often become quite fertile after weathering has broken the lava into fine soil. Some lavas, such as the glassy lava called perlite, are heated in furnaces. They expand into a frothy material used to manufacture lightweight concrete.
There are two kinds of lava: one that is viscous or sticky and moves slowly like thick molasses and a second kind that is so fluid that it flows faster than man can run. Both types form a crust of rock.
At times the liquid lava inside the crust cracks the hardened lava surface into many rough blocks that drag and tumble along as the lava creeps down the side of a volcano.
Other times the lava breaks a hole through the rocky crust and flows through, leaving a huge lava cave or tunnel.
The islands of Hawaii are a chain of volcanoes built mostly of lava. The mountain belt of southern Mexico, with its hundreds of volcanoes, also has a great lava pile.
In Idaho, in the area of the Craters of the Moon, a person can walk into many lava caves that were formed only a few thousand years ago. The surface of such lava is covered with many wrinkles.
Many regions of the earth are made up of piled up sheets of lava. In the northwestern United States, the Columbia lava plateau is made up of a great lava pile more than 5,000 feet thick in places.
Igneous rock, also known as magmatic rock, is formed by the cooling of melted material called magma. Magma is created as a result of great temperature and pressure deep in the earth.
Magma is lava. The magma that cools quickly may form a glassy type of rock which includes obsidian. Magma that cools more slowly may form extrusive rock that consists of large crystals of such material as quartz, feldspar or pyroxene.
The temperature of extruded magma has been measured as high as 2,500 degrees Fahrenheit.