Volcanoes are unpredictable structures that exist in nature, that may look innocuous to those who live in areas that have these, but can be quite deadly whether active or dormant. There are many regions that experience eruptions, with some being less destructive than others, depending on how they erupt and how close they are to towns and neighborhoods. A shield volcano is one kind of three main types of volcanoes, with the other two kinds called stratovolcanoes and cinder cones.
A shield volcano is one that erupts and causes lava flow where it lays itself out in a flattened spread that looks very much like a warrior's shield. Stratovolcanoes are the kind of volcanoes that consist of layers of tephra and lava, that strategically place themselves to form symmetrical cones with sloping sides. The last of the three kinds are called cinder cones, which are erected when lava breaks away into pieces that are skyrocketed upwards from the pressure built up within the volcano. These then fall back onto the earth and cool off before forming the volcano's surface. The cinders thereafter collect around the vent of the volcano, where the cone shapes then form, giving it its name.
An active shield volcano that goes by the name Nyamuragira is a destructive creation in nature, that last erupted in the years 2010 and 2011 respectively. People do not stay around the volcano's periphery, but the national park that is situated close by is affected most by smoke and ash that the volcano gives off. It is located in Africa and is a big tourist attraction that has over the years, formed smaller volcanoes that were short-lived post eruptions from the volcano's flanks. It is a gigantic high-potassium basaltic shield volcano that releases a huge amount of sulfur dioxide upon eruption.
Understanding the Workings of a Shield Volcano
Shield volcanoes are made up of thin basalt lava in thousands of layers where the lava is thick and quite slow-moving, making it spread out quite evenly over the surface, a distance off from the vent. These can be explosive only if water were to get in through the vent. The lava when released through the vent, is hot, where the magma flow is quite abundant. There are little changes made to the lava after it has been expelled, where most of its mass is more lava than pyroclastic material. These volcanic eruptions occur when gas from water vapor along with heat rise up from the earth's core, and combine together to build-up to what is then spewed out. Rock, in turn, due to the presence of the intense heat, turns into magma, where the gas then increases the internal pressure within the volcano, forcing its contents through the vent.
The lava makes its way up from deep within the ocean's bed, right up to the surface of the plates drifting above where the shield volcanoes are then formed. Due to the accumulation of the previously mentioned basalt lava, it forms these slightly sloped ends making up the volcano's outward shield-like appearance. Once these sheets cool down, they spread over large distances before forming layers of the volcano.
Shield volcanoes occur in and around mid oceanic ridge areas. Hawaii is an island that comprises five volcanoes fused together, with some of the volcanoes not yet extinct even today. The island has shield volcanoes that are well-known for erupting on and off during the past couple of years.
The infamous Mauna Lao, which is the main volcano on the 'Big' island, is the highest in elevated structures than any other mountain on the earth, with a staggering height of 30,000 feet from the ocean bed to its top most peak. It is true that Mt. Everest has been given the title as the highest peak (above land), but it is actually Mauna Lao that supersedes it in ranking because as a whole it tops off as the highest mountain. Shield volcanoes are quite abundant here in the tropical islands of Hawaii where they aren't as eruptively violent as their other volcanic counterparts from the group of five volcanoes. The most active of these to still exist in Hawaii is Kilauea which is also a shield volcano that makes up the five volcanoes of the island blend.
This should give you a better understanding on how shield volcanoes are formed and what characteristics are brought to the fore as part of their kind.