Hawaiian Volcanoes

...

While it is known that the lava is more fluid type composition, it is important to understand the source of magma. Due to earthquakes underneath the Kilauea volcano, the magma of Hawaiian volcanoes is thought to form at shallow depths within the Earth. To be more specific, because magma can deform without causing earthquakes, the distribution of the earthquakes under Kilauea and the absence of earthquakes in that zone determines that magma originates within 50-80 kilometers below the volcanic summit in Hawaii. Another factor to consider in the composition of magma is the titling ground on the volcanoes. Since, it is known that magma forms at the shallow reservoir, and the ground is tilted at Kilauea, it can be stated that the movement of magma from the deep to shallow sources is continuous; however, the eruptions do stop once the surface eruption rate exceeds the continuous movement between the deep and shallow sources. These unusual and even unanswered qualities in magma sources are what make the volcanoes of Hawaii stand out (Stovall, 2011).

Once the magma rises to the surface, pressure increases at the vent and an explosion can occur. The explosions of volcanoes cause fragmental substances to be ejected from volcanoes, and these materials are known pyroclastic materials. Common pyroclastic materials formed from fluid eruptions are bombs or blocks. The bombs take on different shapes and sizes. When they are first in the air, some of them are spherical, while others are long and thin in the shape of ribbons. However, the bombs are composed of fluid molten and once they hit the ground some of them flatten out. Once flatten they are given the name pancake bombs, which are common of Hawaiian eruptions. Other common, but unique Hawaiian pyroclastic materials are known as Pele’s hair and Pele’s tears (Pele beings the Hawaiian goddess of volcanoes). Lava fountains throw up drop shape bits that broaden at one end and thin out at the other point, and these drops freeze very quickly, consist of glass and are usually black in color known as Pele’s hair. The lava fountains also produce thin threads of viscous liquid that freezes into slender glassy fragments known as Pele’s hair (Moore, 1992).

The pyroclastic materials also lead to formation of structures such as cinder cones, spatter cones, ash cones and tuff cones. These cones are formed due the fragments of the pyroclastic materials falling around the vents of the volcanoes and develop the appearance of a crater. The pancake bombs are the main materials responsible for the spatter cones and the spherical and ribbon bombs are responsible for the cinder cones. Since Hawaiian eruptions are known for fluid-like magma, the spatter cones are most common. Ash and tuff cones are closely related, as a tuff cone is the final result of an ash cone. While most volcano eruptions in Hawaii are magmatic eruptions and are much more calm, some of the eruptions near the seashore are more explosive due to the magma collaborating with the sea water in the pores of the rocks close to the surface. Therefore, these eruptions create ash due to the mixture of magma, steam and of ash, which forms ash cones, and once the ash is transformed into a light, porous rock known as tuff, tuff cones are formed. Ash and tuff cones tend to be larger in size and saucer-shaped, and the best example of this is Diamond Head in Waikiki. Diamond Head not only is a clear example of an ash and tuff cone, but it also shows how wind can affect the shape by dispersing more ash to one side and creating a high cone on one side. While, most volcanoes in Hawaii are spatter cones, all four types of cones are present on the islands (Macdonald, 1970).

REFRENCES

Coombs, M. (2006). “Growth and Collapse of Hawaiian Volcanoes.” J.Volcanol.Geotherm.Res.,

151(1),.

Lipman, P. (2011). “Early Growth of Kohala Volcano and Formation of Long Hawaiian Rift

Zones.”Geology (Boulder), 39(7), 659-662.

Macdonald, G. A. (1970). “Volcanoes in the Sea; the Geology of Hawaii.” Volcanoes in the Sea;

the Geology of Hawaii, .

Moore, R. B. (1992). “Volcanic Geology and Eruption Frequency, Lower East Rift Zone of

Kilauea Volcano, Hawaii.” Bulletin of Volcanology, 54(6), 475-483.

Stovall, W. K. (2011). “Eruption Dynamics of Hawaiian-Style Fountains; The Case Study of

Episode 1 of the Kilauea Iki 1959 Eruption.”Bulletin of Volcanology, 73(5), 511-529.

Wenkam, R. (1987). “The Edge of Fire; Volcano and Earthquake Country in Western North

America and Hawaii.” The Edge of Fire; Volcano and Earthquake Country in Western North America and Hawaii.