Explosive volcanoes are developed from a blockage within the volcano. These volcanic eruptions are violent and sudden. The cause for these explosions is viscous magma that releases intense gasses and pressure into the volcano with no escape, the pressure builds and the explosion occurs. These volcanoes appear to be mountains when inactive. This type of explosion leaves a billowing cloud of volcanic ash and debris. Explosive volcanoes are dotted all over the globe but most commonly occur on boundary's of tectonic plates.
Effusive volcanoes occur when (1200C) basalt magma makes its way up the earths crust, breaks through to the surface through vents, and flows slowly onto a sloping hill flowing along the surface of the earth. This eruption looks like taffy loosely spreading. This is the type of volcano most commonly seen in Hawaii.

Magma works its way up from the earths upper mantle towards the surface through chambers in the earths crust. Because magma is lighter and less dense than the rock surrounding it, magma rises and collects in the chambers underground. These chambers become filled and heated to the point of eruption. The eruption is the product of an intense pressure build. Once the magma gets to the surface of the earth the lava will either be blown out of one explosive volcano or it will flow in a lava field slowly. no matter what way the magma erupts, the volcano will increase in size.

Volcanic eruptions cause a multitude of negative effects to the atmosphere. The gasses released by explosive volcanoes aids in the greenhouse effect by adding Co2 into the atmosphere. The ash and sulfur oxides in these explosions block out the sun and actually cool the earth by deflecting sunlight in the atmosphere, sometimes reaching to the stratosphere. The ash and debris as well as effusive explosions cause harm directly on land as the eruption is happening. The immediate effects of the ash and debris is the evacuation of many living things in the area, the ash is like breathing in extremely thick black smoke causing respiratory problems and makes the soil unusable for thousands of years as well. All things on earth are effected in the event of a volcanic eruption.

Throughout the earths history there have been volcanic explosions that have killed entire ecosystems on entire continents. Volcanos are measured on the Volcanic Explosivity Index 1-8. Each number on the scale representing a 10x greater explosion than the previous number. The first human witnessed documented volcanic eruption was around 4000 years ago. In 1929, Santa Maria volcano located in Guatemala, spewed a pyroclastic magma (hot wall of burning rock and debris) which killed as many as 5,000 people. Another famous volcano is Yellowstone. Three magnitude-8 eruptions rocked the area 2.1 million years ago, 1.2 million years ago, and most recently 640,000 years ago. Over the earths history we have experienced large and devastating volcanic eruptions, the only question that remains is: when will this happen again?

There is no doubt that volcanic eruptions will continue into the future. Currently effusive volcanoes are spreading across Hawaii at a rapid and devastating rate. The Yellowstone volcano now has a 1/700'000 chance of happening today and the odds will continue to increase each day. Scientists have discovered a huge region of magma underground that would produce enough magma and ash to fill the Grand Canyon 11 times. It is inevitable that we are going to experience volcanic eruptions in the future.