Earth Systems and its Impact on Hawaiian Geography and Topography
The Earth system is a complicated random actions caused by several interrelated factors. These proceedings affect the kind of topography regions in the Earth has, and this in turn has parallel effects to the type of ecosystems and species these regions have. One of the features and results of the Earth’s dynamic systems are island formation due to volcanic activities.
This is an important scenario since the isolation and the specific type of environment these islands or the groups of islands undergo allowed them to create rare categories of flora and fauna that adds up to the growing trend of speciation all over the world, thus contributing to biodiversity. The Earth is divided into two distinct parts which are the asthenosphere and the lithosphere and this division is based on the mechanical differences of these two parts. Moreover, the disparity between the two is highlighted on their mode of heat transfer.
Mechanically, the lithosphere is rigid and being far from the Earth’s center, it is also cooler, compared to the asthenosphere which is closer to the center making it hotter and thus allowing for a less inflexible composition. The lithosphere is made up of both the crust and the mantle, but depending on various situations such as temperature and pressure fluctuations or shear strength, the mantle can either be a part of the lithosphere or to that of the asthenosphere (Marti and Gerald).
The central theme of the plate tectonics theory that explains how the Earth came to be as it is now is that, both the lithosphere and the asthenosphere are separate tectonic plates with varying rigidity and strength, making the lithosphere floats over the fluid like asthenosphere. These movements are either through the oceanic crust, the continental crust or the combination of both. The difference between the two are in their composition wherein oceanic crusts are made up of heavier elements particularly silicon and magnesium; thus making it to stay below sea level.
Moreover, the crust that projects above the sea is the continental crust and is constituted of silicon and aluminum. These plates are able to move because of the drastic dissimilarity between the density and weight of the oceanic crust and the relatively weak asthenosphere (Marti and Gerald). When a plate meets another plate in a plate boundary, then various geological events take place such as earthquakes, mountain formation, initiation of a volcanic ridge and ocean trenches. The synergy between two plates or other several minor plates create seismic (earthquake) zones accompanied by volcanic activities.
The Pacific Ocean is encircled with such a zone more popularly known as the “ring of fire”. As the Pacific plate moves northwest, it bends then enters a subduction zone creating earthquakes and volcanic activities in Japan, the Aleutian Trenches and in Kamchatka near the Eurasian continental plate. Three of the main types of plate boundaries are the transform boundaries, divergent boundaries and the convergent boundaries. Transform boundaries are plate edges where two plates grind each other moving in different directions; an example of such is the St, Andreas Fault in California.
Divergent boundaries on the other hand, as the name suggests is the place where two opposing plates slide past each other; these are also the area where plates are rifting each other. And lastly, the convergent boundaries more popularly referred to as the subduction zones where the plates slide and one of the plates folds underneath the other one. The powerful drive of the plates towards the subduction zones allows the thicker plate to pierce through the hot and more viscous asthenosphere.
This complex mechanism of the ascending magma and fluid released in the subduction zones ultimately forms island arcs. During the convergence of the lighter continental crust and the heavier oceanic crust, the oceanic crust stabs through the asthenosphere thus bursting out magma and forming volcanic ridges and arcs in the opposite continental plate. On the other hand, when two continental ridges converging towards each other they form mountain ridges; an example is the Himalayas, wherein the Indian plate is being plunged under by the nearby Euarsian plate.
In subduction zones aside from the formation of island arcs constant rise of magma due to the regular stab of the heavier mantle towards the hotter mantle material wells up and create a hot spot. Hot spots are located above the mantle plumes, wherein the process of convection in the mantle creates a tower of hot materials. This rising mantle material could form a plume reaching up to 1000 kilometers wide above the surface of the Earth. As solid rock transforms into liquid rock due to the rise in temperature, it thus becomes less dense relative to the solid rock around allowing it to rise above and be pushed with a great force.
In the process of travelling upward, it melts other rock along the way and thus adding more magma to it. This rising magma creates up what scientists refers to as magma chambers and given the appropriate amount of energy and pressure, it cracks the surface open to an eruption. Once magma is out in the surface of the Earth it is now termed as lava and this lava forms the volcano. The shape of the volcano is dependent on the materials composing the magma at the same time the intensity of the eruption (Marti and Gerald).
There are many types of volcanic eruptions; some volcanoes erupt violently while some release off lava slowly and constantly; again this difference is caused primarily by the difference in lava viscosity and percentage of gas content. If the magma is more viscous thus resisting flow, the gas bubbles will have difficulty to escape adding up to the higher pressure making eruptions more violent (Marti and Gerald). While on the other hand, less pressure and less violent explosion is expected if the magma is more fluid allowing gas bubbles to break out as the magma moves up.
The varying viscosity is reliant on the amount of silicon content of the magma and to the general type of materials the mantle is composed of. In general, the major types of volcanic eruptions are the Plinian, the Strombolian, and the Hawaiian. Plinian eruptions are very forceful explosions with magma that are highly viscous and with very high gas content. This strong upwards thrust of pressure can propel pyroclastic material up to 48 kilometers above the surface at the speed of hundred feet per second.
Also a distinction of this type of eruption is the towering eruption plume containing high level of tephra (solid volcanic material). Secondly, strombolian volcanoes are not as strong a plinians, with their fairly viscous magma composition but only in little amount the thrust goes only as high as 9 meters. These types of eruptions also produce less tephras travelling at slower velocities. Finally, Hawaiian eruptions are not violent and less destructive since they don’t throw up pyroclastic materials therefore producing a slow but steady flow of less viscous magma.
These types of eruptions have the famous lava lakes, wherein the steady lava flows construct into huge lakes of lava from the craters themselves or into other nearby depressions (Marti and Gerald). All volcanoes, including the 80 identified those found underwater comprising the Hawaiian-Emperor seamount chain which stretches for 3,600 miles from the Aleutian Trench to the Lo’ihi seamount (the youngest volcano in the chain) are shield volcanoes (Clague, Moore, and Reynolds). A shield volcano is classified according to its shape, and got its name from the Icelandic word “Skjaldbrei?
ur”, which means “broad shield”. These types of volcanoes are formed from lava flows of very low viscosity and after a history of constant eruptions they built up on top of each other. Moreover, shield volcanoes have distinct features called calderas which are different from the craters plinian or strombolian volcanoes have. Calderas are formed from the collapsed of land on the mouth of a volcano above the magma chamber, during an eruption. In the formation of shield volcanoes, the caldera repetitively settles then re-fractures as the magma moves out then refills as the magma comes in again.
One of the most notable volcanoes in Hawaii, is Mauna Loa, and not only is it the largest volcano comprising the whole island of Hawaii but more importantly it is the largest in the world. Lava coming out of its vents is comprised of less percentage of silica making the flow very fluid with less trapped air bubbles allowing for passive eruptions (Tarduno, et. al. ). This characteristic of eruptions became a template for other volcanoes with similar traits from most of the volcanoes found in Hawaii thus earning the name Hawaiian type of eruptions as discussed above.
Mauna Loa and the other volcanoes in the main Island of Hawaii started as a hot spot, or a constant surge of hot magma up to the Earth’s surface (Tarduno, et. al). Although this hotspot is fixed in position, the Pacific plate which is ne of the major rift in this subduction zone are moving at a rate of 4 inches annually. This Hawaiian hotspot has been responsible for the emergence of the Hawaiian island chain and currently it now located under the Island of Hawaii the end of the Hawaiian Emperor Chain (Tarduno).
The volcanoes along this chain were once over the hot spot but the movements of the Pacific plate pulled the hotspot’s magma source away, thus the islands and the seamounts are older going northwest. Another interesting fact with the Hawaiian Hotspot is that, the magma contributing to it comes from deep mantle magma in contrast to the shallow origin of the mid-oceanic ridge. This idea is essential in understanding why the supply and the composition of the magma released by the volcanoes along the chain differ as plates move through in tectonic motion (Sharp and Clague).
This variation largely influenced the distribution of floral and faunal species over this Hawaiian Emperor Chain. When we say that a species is endemic to a place, then it is similar in saying that that species is unique and can only be found in that specific place. Endemism is a phenomenon distinct only in discrete geographical places The Hawaiian group of islands located almost 4000 kilometers from the nearest main land, is probably the most isolated group of islands in the world.
Flora and fauna species in this group of islands is a result of early and occasional arrival of certain species and their evolution and adaptation over a period of 70 million years – isolated form the rest of the world. As a result, the Hawaiian chain of islands houses a huge variety of endemic species. Some of the islands were above the sea for a roughly 10 millions years which is not enough time for biological evolution in the archipelago explaining the great differences between the kinds of species found in each islands.
Several modes of species propagation and transfer that secured the unique characteristic of floral and fauna in the Hawaii are through migrant birds or through insects carried by high winds. This species introduced in an isolated island were then forced to adapt. This will then narrow down the gene pool and at the same time the population of the colonizing species will them differ from the original and thus contribute to a new population (Wagner and Funk). Here is a short history of the possible sequence of events in a typical Hawaiian island.
First is the island formation then the first colonizers are the plants since transport through wave action or through winds is easier. After a few millions of years, a biota is then established and after a few more thousand of years, this biota stabilizes. As the island moves away from the hotspot disruption occurs and speciation follows in order to fill the emptied niche. The isolation will then develop endemic species and the pattern of speciation is reflected by the sequence of the islands.
Usually, extreme isolations limits the vertebrate fauna in the island, in fact some seamounts lack a native amphibian or a native reptile (Wagner and Funk). The main Hawaiian Island on the southern end of the Emperor Seamounts and the Northwest Hawaiian Island Ridge built on the succession of different types of magma from the drifting hotspot creating various distances among the islands and variance in the type of soil and rock composition along this chain manipulate much of the Hawaiian ecosystem, and the evolution of plant and animals species over the island (Xu, et.
al). The landscape changes over the islands as a result from the eruption of these volcanoes destroys an ecosystem then allows for the growth of a new community; this on the other hand has great impact to the degree of speciation and to the extinction of a species. To trace up the difference, millions of years ago, the islands along these chain are small and widely spaced, very much different from the current topography of the islands which are large and closer to each other. This observation can account for the either the ease or the difficult in migration of the species.
Other volcanoes and seamounts into combines into a single island, other was able to provide bridges but all of these were eroded by wave action or through other mechanical actions. Diversity was lost from the older island or was prevented to migrate to the other newer islands. Also, localized species, or those that thrive in a specific community could be eliminated very easily in a single disturbance such as lava flows, even before given the chance to cross other islands (Price and Clague).
Dispersal and speciation can only occur given a long period of time allowed for differentiation, so given the short phase that occurred after the destruction of a community due to volcanic activity, the animal and floral species in these islands must be a result of recent colonization form outside these chain of islands and a divergence of the present day floral and faunal gene pool. This idea was invariable with the recent phylogenetic findings on the island which shows that 12 of the 15 species in the high islands have diverged within a lifetime and three of these twelve have colonized the chain during this period (Price and Clague).
The history of volcanism on the island of Hawaii particularly in the Hawaiian mainland resulted to the different elevations all over the island. Bathymetric data have shown that none of the earlier islands among the island chain attained the height of the Mauna Loa or Mauna Kea. Higher islands have surprising biological diversity in contrast to the lower lands, and these differences can be accounted for the elevation itself, rainfall pattern (with direct parallel relationship to elevation) and the mixture of topography and land features.
Species endemism is very high in the islands of Hawaii as a result of biological isolation brought about by the movement of the Hawaiian Hotspot that is, some species are strictly found in other island and not in the others. Higher islands are also younger from the recent lava flows providing for dissimilarity with the species found in lowlands. But aside from the prevalent endemism on the islands, genetic evidences also suggested that some of the species in higher and newer islands evolved from the ancient line of species originating from the older islands (Carson and Clague).
These types of species may have been dominant species equipped with adaptations allowing them to migrate easily to other nearby islands, its analog are similar to those species that colonize lava flows (where dynamic genetic change is prevalent). The island of Hawaii, remain in isolation to different species of animals for the last million of years a result to the movement of the hotspot away and away from the mainland which is the source of more species. As a result, Hawaii became a home of rare and a few endemic species.
The different elevations created by the constant volcanic activity in the island produce different types of niche for both flora and faunal species. Today, Hawaii is a popular tourist destination that provides both cultural enrichment and natural or environmental appreciation to tourists. Not only did it provide and arena where people can see adaptive radiation in action, the species that evolve in the island dictates the time of culture that progressed in Hawaii.
Truly the distinct isolation of the volcanic islands of Hawaii nurtured a culture very much different from the neighboring countries and civilization as evident by language, writing system, religion, music, architectures (heiau temples) and distinctive art such as the hula dance. All of these topographical features and uniqueness of the Hawaiian Islands can be attributed to its exclusive geography resulting from the different interactions of plate movements, volcanism, mountain building and other types of Earth processes dictating the whole evolution of the islands.
Carson, H. L and D. A. Clague. Geology and biogeography of the Hawaiian Islands, In: Hawaiian Biogeography: Evolution on a hot spot archipelago, W. L. Wagner and V. A. Funk, eds, Smithsonian Institution Press, DC. , 14-29. 1995. Clague, D. A. , J. G. Moore, and J. R. Reynolds. “Formation of submarine flat-topped volcanic cones in Hawaii. ” Bulletin of Volcanology, 62 (2000): 214-233. Diamond, Jared. Guns Germs and Steel. W. W. Norton, 1997 Haraldur Sigur? sson, ed. Encyclopedia of Volcanoes.
Academic Press, 1999. Marti, Joan and Ernst, Gerald. Volcanoes and the Environment. Cambridge University Press. 2005. Price, J. P. , and D. A. Clague. “How old is the Hawaiian biota? Geology and phylogeny suggest recent divergence”, Proceedings of the Royal Society of London, 269 (2002): 2429-2435. Sharp, Warren D. ; Clague, David A. “50-Ma initiation of Hawaiian-Emperor bend records major change in Pacific Plate motion”. Science 313. 5791 (2006): 1281–1284. Tarduno, John A. ; et al. (2003).
“The Emperor Seamounts: Southward Motion of the Hawaiian Hotspot Plume in Earth’s Mantle”. Science 301. 5636 (2003): 1064–1069. Wagner, W. L. and V. A. Funk. Hawaiian biogeography: evolution on a hot spot archipelago. Smithsonian Institution Press, Washington, D. C. (1995) Xu, G. , F. A. Frey, D. A. Clague, D. Weis, and M. H. Beeson. “East Molokai and other Kea-trend volcanoes: Magmatic processes and sources as they migrate away from the Hawaiian hot spot,” Geochem. Geophys. Geosyst (2005).Sample Essay of Eduzaurus.com