All volcanic eruptions are not alike. Some eruptions are quiet, with lava slowly oozing from a vent. Other eruptions are very violent, with lava and other materials being hurled hundreds of meters into the air. Gases from within the Earth's interior mix with huge quantities of volcanic dust and ash and rise into the air as great dark clouds that can be seen from many kilometers away. A violent volcanic eruption is truly an awesome sight.

Although it seems to be a dangerous endeavor, many scientists spend their working lives studying volcanoes. For volcanoes are "windows" into the interior of the Earth. By analyzing the mineral makeup of lava, geologists can determine the chemical composition of the magma from which the lava formed. Such data provide information about the composition of the part of the Earth that remains unseen. There are four main types of lava.
 

Volcanic Lava
One type of lava is dark-colored and contains a lot of water. This lava is rich in the elements iron and magnesium. When this type of lava cools, igneous rocks such as basalt are formed.

Another type of lava is light in color. This lava, which contains little water, is rich in the elements silicon and aluminum. Compounds of these elements account for its lighter color. When this type of lava cools, it forms the igneous rock rhyolite, which has the same composition as granite.

The third type of lava has a chemical compostion between that of the dark-colored type and the light-colored type. Different varieties of igneous rocks in the Earth's crust, such as andesite are formed form this type of lava.

The fourth type of lava contains large amounts of gases such as steam and carbon dioxide. When this lava hardens, it forms rocks with many holes in them. Holes in this type of lava form as gas bubbles are trapped in the molten rock as it hardens. Pumice is an igneous rock formed from this type of lava.

Volcanic Fragments
During volcanic eruptions, many rock fragments are blown into the air. The smallest particles are called volcanic dust. Particles of volcanic dust are very fine, less than 0.25 millimeter in diameter, or as tiny as grains of flour.

Rock particles more than 0.25 millimeter but less than 5 millimeters in diameter are called volcanic ash. Particles of volcanic ash are about the size of rice grains. Volcanic ash falls to the Earth's surface and eventually forms small rocks. Both volcanic dust and volcanic ash can be carried away from a volcano by the wind.

Larger rock particles are called volcanic bombs. Volcanic bombs are a few centimeters to several meters in diamter. Some bombs are the size of boulders and have masses of several metric tons. Small volcanic bombs about the size of golf balls are called cinders. When volcanic bombs are hurled out of a volcano, they are molten. They harden as they travel through the air.

The mythical goddess Pele

Described as "She-Who-Shapes-The-Sacred-Land" in ancient Hawaiian chants, the volcano goddess, Pele, was passionate, volatile, and capricious. In modern times, Pele has become the most visible of all the old gods and goddesses. Dwelling in the craters of the Big Island's Kilauea Volcano, she has been sending ribbons of fiery lava down the mountainside and adding new land around the southeastern shore almost continuously since 1983.

Pele was born of the female spirit Haumea, or Hina, who, like all other important Hawai'i gods and goddesses, descended from the supreme beings, Papa, or Earth Mother, and Wakea, Sky Father. Pele was among the first voyagers to sail to Hawai'i, pursued, legends say, by her angry older sister, Na-maka-o-kaha'i because Pele had seduced her husband. Pele landed first on Kaua'i, but every time she thrust her o'o (digging stick) into the earth to dig a pit for her home, Na-maka-o-kaha'i, goddess of water and the sea, would flood the pits. Pele moved down the chain of islands in order of their geological formation, eventually landing on the Big Island's Mauna Loa, which is considered the tallest mountain on earth when measured from its base at the bottom of the ocean.