What Products Come Out of a Quiet Volcanic Eruption?

Setting the Stage

• When temperatures under the surface of the earth get extremely hot, part of the crust, earth̵7;s top layer, or mantle, the next layer, can melt. The melted rock contains gases, and liquid material, magma, that spews or flows onto the earth̵7;s surface through a hole called a volcano. Many variables contribute to eruptions, especially the buoyancy of the magma. If it̵7;s a lot less dense than the rock around it, the magma will rise toward the earth̵7;s surface. As magma rises, some of its contents, such as water, turn to gas. This increases pressure and helps push the magma out. Once it's on the surface, magma is called lava. Eruptions can be relatively quiet, effusive, or explosive.

Go with the Flow

• During an effusive eruption, a great deal of lava flows onto the area surrounding the volcano. This lava consists of about half silicon dioxide with significant amounts of iron, magnesium and sodium. The lava is relatively thin and fluid, which allows it to move easily. Spreading quickly, the lava can look like smooth ropes or wide sheets. This movement can create ̶0;shield volcanoes,̶1; which are characterized by broad, gentle slopes. The Hawaiian Islands contain this type of volcano.

Hot, Hot, Hot

• One of the products of a volcano eruption is heat. However, the lava in a gentle eruption is far hotter than in explosive ones. Before it hits the surface, the magma from a quiet eruption is between 800 and 1,000 degrees Celsius. Temperatures for an explosive eruption start as low as 650 degrees Celsius. Heat affects how a substance can flow. The high temperature of lava in a quiet eruption helps the lava flow readily. Think of it like this--ice cream that̵7;s been sitting out for several minutes is mushy and slides slowly off your spoon. However, if the dessert is room temperature, it̵7;s liquid and flows easily.

It's a Gas

• A quiet eruption releases many gases, primarily water vapor and carbon dioxide. Because the magma that leads to quiet eruptions is comparatively thin and liquid, the eruptions have far less gas than the explosive type. When the magma flows easily, gases can expand. At the surface they are not trapped by solids, so gases simply flow into the air rather than forcefully bursting free. Often, quiet eruptions form fire fountains that are impressive but not violent. As the gases emerge they can carry liquid lava skywards hundred of yards.