Types of Volcanic Landform: Shield Volcanoes

Mauna Loa Volacano,Hawaii Volcanoes National Park, Hawaii, USA

Shield Volcano is atype of volcano usually built almost entirely of fluid lava flows. They are named for their low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid (low viscosity) lava they erupt which travels farther than lava erupted from stratovolcanoes. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. The shape of shield volcanoes is due to the low viscosity of their mafic lava.

Shield volcanoes are distinguished from the three other major volcanic archetypes stratovolcanoes, lava domes, and cinder cones by their structural form, a consequence of their unique magmatic composition.

A shield volcano is usually built up from highly fluid magma flows, which results in a volcano with a low profile that is spread over a large area, similar to the shield of a warrior if it were lying on the ground. The width of a shield volcano is usually 20 times its height, on average, but that doesn't mean that they do not reach high altitudes. Shield volcanoes can form from one single long-term eruption or over the course of several eruptions. Many of the shield volcanoes on earth are located in Hawaii, including Hawaii's volcano Mauna Loa which is considered to be the second largest volcano on earth, next to Tamu Massif in the Pacific Ocean.

Because of the variety of formation, you will see slightly different shapes in the various shield volcanoes around the world. The ones in Iceland, for example, are generally much smaller in size and almost perfectly symmetrical while those found in Hawaii are much larger (think of Mauna Loa) and elongated. The shields found on the Galapagos Islands are different from both of these, having flat tops, steep middle slopes and deep calderas at the summit. These differences not only show variations in formation but also in the eruption types generally found in the region.

Hawaiian Volcanoes

Hawaii is home to a great deal of the planet’s shield volcanoes as the Pacific Plate and the Hawaii hotspot have combined to form a large chain of various volcanoes of all types. This chain includes more than 43 major volcanoes, including Mauna Loa. As mentioned earlier, Mauna Loa is the largest shield volcano. It is also Hawaii’s highest volcano, reaching 4,170 meters above sea level in addition to traveling 13 kilometers down below the waterline. This volcano has most likely been eruption for over 700,000 years and the most recent eruption took place in 1984.

Iceland

Another place that you can find multiple shield volcanoes is in Iceland. The shield volcanoes found there usually range from 5,000 to 10,000 years old. These volcanoes are also usually smaller than those in other locations and are generally symmetrical and their eruptions usually occur from their summit calderas.

Galapagos Volcanoes

Another area with a great deal of shield volcanoes is the Galapagos Islands, with the volcanoes ranging from 700,000 to 4.2 million years old. Several of the islands are in fact shield volcanoes, such as Fernandina. This shield volcano has steep upper flanks but low-angle lower flanks. It has been currently erupting since April of 2009.

In terms of composition, the lava flows found in the Galapagos Islands are very similar to those in Hawaii although unlike other sets of volcanoes formed by one hotspot, they do not create a line.

Characteristics Of A Shield Volcano:

A very broad and gently sloping volcanoes
This volcano generally have an Basaltic Lava;a type of lava that have very low amounts of silica,making it flow in great distances over the wide surface of the volcano
The slope is usually more than 10 degrees at it's summit and 2 degrees at it's base.

Parts of a Shield Volcano

Central Vent-A central vent is an opening at the Earth's surface of a volcanic conduit of cylindrical or pipe-like form.

Summit Caldera-Caldera The Spanish word for cauldron, a basin-shaped volcanic depression; by definition, at least a mile in diameter. Such large depressions are typically formed by the subsidence of volcanoes.Kilauea caldera(formed in 1790) is called Halemaumau.

Magma Reservoir-An underground zone of porous rock containing magma.

Mauna Loa in Hawaii is the One of theFamous Shield Volcano in the world.Mauna Loa, world's largest mountain and volcano, is a archetype of a basaltic shield volcano in its late mature stage of life, and only about 600,000-1,000,000 years old. Although not erupting as frequently as its younger neighbor Kilauea, it is also one of the most active volcanoes of the world. When it erupts, its eruptions are usually huge and produce large rivers of lava that have repeatedly threatened the town of Hilo.

Mauna Loa's most recent eruption occurred from March 24 to April 15, 1984. No recent eruptions of the volcano have caused fatalities, but eruptions in 1926 and 1950 destroyed villages, and the city of Hilo is partly built on lava flowsfrom the late 19th century.