{"id":143502,"date":"2013-10-29T13:59:42","date_gmt":"2013-10-29T12:59:42","guid":{"rendered":"http:\/\/www.madrimasd.org\/blogs\/universo\/?p=143502"},"modified":"2013-10-29T13:59:42","modified_gmt":"2013-10-29T12:59:42","slug":"relieve-de-las-islas-volcanicas-erosion-disolucion-colapso","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2013\/10\/29\/143502","title":{"rendered":"Relieve de las Islas Volc\u00e1nicas: Erosi\u00f3n, Disoluci\u00f3n, Colapso"},"content":{"rendered":"

En 2011 publiqu\u00e9 un art\u00edculo sobre la edafogeograf\u00eda insular<\/a> en que entre otros archipi\u00e9lagos<\/strong> <\/span>se analizaba el de Haw\u00e1i<\/strong><\/span>. Hace unos meses le\u00ed\u00a0una nota de prensa que hac\u00eda referencia a otro \u201cpaper<\/em>\u201d cuyo t\u00edtulo me pareci\u00f3 sugestivo. \u00a0Sin embargo, ha resultado ser una trampa (mucho tiempo gastado en vano). Es decir, su contenido es interesante y sorpr\u00e9ndete, por lo que poco os puedo decir al respecto, tras analizar la bibliograf\u00eda. Mis lecturas sobre el ciclo de vida de los sistemas insulares sobre puntos calientes del manto terrestre<\/strong> <\/span>hac\u00edan \u00e9nfasis en que la desaparici\u00f3n de las islas se deb\u00eda m\u00e1s al colapso de los edificios volc\u00e1nicos, incluidos grandes deslizamientos<\/strong><\/span> (generalmente submarinos) de tierras que afectaban porciones enormes de sus respectivos espacios geogr\u00e1ficos.<\/strong> Sin embargo, la nota de prensa<\/strong> <\/span>que acabo de leer y que os muestro abajo, defiende que, al menos en algunos casos, es la erosi\u00f3n la que progresivamente va allanando sus relieves que finalmente terminan sumergidos bajo el oc\u00e9ano<\/span>. No obstante<\/span><\/strong>, la originalidad de la isla de \u00a0hawaiana de Oahu<\/strong> <\/span>parece estribar en que se ha constatado, mediante estudios geoqu\u00edmicos, que la disoluci\u00f3n de sus rocas que arrastra los materiales disueltos hacia las aguas subterr\u00e1neas puede ocasionar una p\u00e9rdida del relieve mayor que la debida a la erosi\u00f3n en sentido estricto<\/strong> <\/span>(arrastre de materiales hacia el mar por las aguas corrientes, deslizamientos normales, erosi\u00f3n costera, etc.). No hab\u00eda le\u00eddo jam\u00e1s nada parecido, m\u00e1s aun cuando gran parte de los materiales de estos archipi\u00e9lagos son volc\u00e1nicos y preferentemente bas\u00e1lticos.<\/p>\n

\u00a0\"paisaje-ohau-fuente-9wows-waterfalls-oahu-hawaii\"<\/p>\n

Paisaje de la Isla de Oahu fuente 9Wows<\/a><\/p>\n

\u00a0Debe tratarse de la primera evidencia de este tipo de proceso y como corolario, de ser cierto, habr\u00eda que analizar su singularidad\/generalidad en otros sistemas insulares. \u00a0\u00a0En consecuencia no me atrevo a\u00f1adir mucho m\u00e1s al respecto. Abajo os dejo la nota de prensa, fragmentos extra\u00eddos de una p\u00e1gina Web de la Universidad de Haw\u00e1i y otro de Wikipedia. Ser\u00eda sorprendente pero a saber (\u2026). \u00a0Tambi\u00e9n pod\u00e9is saber algo m\u00e1s sobre la geolog\u00eda de la Isla de Oahu<\/a>, y m\u00e1s concretamente su composici\u00f3n geol\u00f3gica<\/a>, pinchando en las palabras hipervinculadas, como tambi\u00e9n de lo concerniente a sus aguas subterr\u00e1neas.<\/a>\u00a0 Sin embargo, no he encontrado referencia alguna a este proceso.<\/p>\n

\"oahu_universidad-de-hawaii\"<\/p>\n

Relieve de la Isla de Oahu: Fuente Universidad de Haw\u00e1i<\/a><\/p>\n

\u00a0<\/strong>Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/strong><\/span><\/p>\n

\"oahu-universidad-de-hawaii\"<\/span><\/p>\n

Ciclo de Vida de Una Isla. Fuente: Universidad de Haw\u00e1i<\/a><\/p>\n

Hawaiian Islands Are Dissolving from Within, Study Says<\/strong><\/a><\/strong><\/h3>\n

\u00a0<\/strong>Dec. 21, 2012<\/em><\/strong> \u2014 Most of us think of soil erosion as the primary force that levels mountains, however geologists have found that Oahu’s mountains are dissolving from within due to groundwater<\/strong>.<\/p>\n

\u00a0Someday, Oahu’s Koolau and Waianae mountains will be reduced to nothing more than a flat, low-lying island like Midway.<\/strong><\/p>\n

But erosion isn’t the biggest culprit<\/strong>. Instead, scientists say, the mountains of Oahu are actually dissolving from within<\/strong>.<\/p>\n

\u00abWe tried to figure out how fast the island is going away and what the influence of climate is on that rate<\/strong>,\u00bb said Brigham Young University geologist Steve Nelson. \u00abMore material is dissolving from those islands than what is being carried off through erosion<\/strong>.\u00bb<\/p>\n

The research pitted groundwater against stream water to see which removed more mineral material<\/strong>. Nelson and his BYU colleagues spent two months sampling both types of sources. In addition, ground and surface water estimates from the U.S. Geological Survey helped them calculate the total quantity of mass that disappeared from the island each year<\/strong>.<\/p>\n

\u00abAll of the Hawaiian Islands are made of just one kind of rock<\/strong>,\u00bb Nelson said. \u00abThe weathering rates are variable, too, because rainfall is so variable<\/strong>, so it’s a great natural laboratory.\u00bb<\/p>\n

Forecasting the island’s future also needs to account for plate tectonics<\/strong>. As Oahu<\/strong> is pushed northwest, the island actually rises in elevation at a slow but steady rate<\/strong>. You’ve heard of mountain climbing; this is a mountain that climbs.<\/p>\n

According to the researchers’ estimates, the net effect is that Oahu will continue to grow for as long as 1.5 million years<\/strong>. Beyond that, the force of groundwater will eventually triumph and the island will begin its descent to a low-lying topography<\/strong>.<\/p>\n

Undergraduate student Brian Selck co-authored the study, which appears in the journal Geochimica et Cosmochimica Acta<\/em>. Unfortunately for him, he joined the project only after the field work in Hawaii took place.<\/p>\n

\u00a0Instead, Selck performed the mineralogical analysis of soil samples<\/strong> in the lab back in Provo. The island’s volcanic soil contained at least one surprise in weathered rock called saprolites<\/strong>.<\/p>\n

\u00abThe main thing that surprised me on the way was the appearance of a large amount of quartz in a saprolite taken from a 1-meter depth<\/strong>,\u00bb Selck said.<\/p>\n

After he graduates from BYU, Selck will pursue a career in hydrogeology. BYU geology professor David Tingey joins Nelson and Selck as a co-author on the new study.<\/p>\n

\u00a0Story Source: <\/strong>The above story is reprinted from materials<\/a> provided by Brigham Young University<\/strong><\/a>. Note: Materials may be edited for content and length. For further information, please contact the source cited above.<\/em><\/p>\n

\u00a0<\/strong>Journal Reference<\/strong>: Stephen T. Nelson, David G. Tingey, Brian Selck. The denudation of ocean islands by ground and surface waters: The effects of climate, soil thickness, and water contact times on Oahu, Hawaii<\/strong>. Geochimica et Cosmochimica Acta<\/em>, 2013; 103: 276 DOI: 10.1016\/j.gca.2012.09.046<\/a><\/p>\n

Por otro lado, en el siguiente sitio web se nos informa de las siguientes caracter\u00edsticas de la Isla de Oahu<\/a>, al margen de su composici\u00f3n calc\u00e1rea<\/strong> (incluyendo formaciones coralinas), bas\u00e1ltica \u00a0y una geomorfolog\u00eda muy variada<\/strong>.<\/p>\n

O\u2018ahu is the third largest Hawaiian island with 180 km of general coastline that contours a highly irregular shape that was greatly influenced by two massive landslides<\/strong>, that removed ~1\/3 of the northeastern portion of the island and aproximately 1\/2 of the western side . Today, the shape of O\u2018ahu is constrained by two great mountain ranges that are the eroded remnants of<\/strong> two separate shields truncated by the prodigious slides<\/strong>.<\/p>\n

The Ko\u2018olau Range (2.7 my in age)<\/strong> runs up the northeast side of the island, perpendicular to the trade winds, whereas the older Wai\u2018anae Range (3.9 my in age) <\/strong>extends along the west side. Moisture rich trade winds are typically pushed across the broad side of the Ko\u2018olaus, maintaining lush vegetation that reaches from the mountains to the coast. In contrast, the Wai\u2018anae Range on the west side is dry<\/strong>, receiving little of the moisture carried by the trade winds.<\/p>\n

Geolog\u00eda del Archipi\u00e9lago Hawaiano seg\u00fan Wikipedia<\/a><\/p>\n

The chain of islands or archipelago<\/a> formed as the Pacific plate<\/a> moved slowly northwestward over a hotspot<\/a> in the Earth’s mantle<\/a> at about 32 miles (51 km) per million years. Hence the islands in the northwest of the archipelago are older and typically smaller, due to longer exposure to erosion<\/a>. The age of the archipelago has been estimated using potassium-argon dating methods.[14]<\/a><\/sup> From this study and others,[15]<\/a>[16]<\/a><\/sup> it is estimated that the northwestern most island, the Kure Atoll<\/a>, is the oldest at approximately 28 million years (Ma); while the southeastern most island, Hawai\u02bbi<\/a>, is approximately 0.4 Ma (400,000 years). The only active volcanism in the last 200 years has been on the southeastern island, Hawai\u02bbi, and on the submerged but growing volcano at the extreme southeast, Lo\u02bbihi<\/a>. The Hawaiian Volcano Observatory<\/a> of the U. S. Geological Survey documents recent volcanic activity and provides images and interpretations of the volcanism.<\/p>\n

Almost all magma<\/a> created in the hotspot has the composition of basalt<\/a>, and so the Hawaiian volcanoes are constructed almost entirely of this igneous rock<\/strong> and its coarse-grained equivalents, gabbro<\/a> and diabase<\/a>. A few igneous rock types with compositions unlike basalt,<\/strong> such as nephelinite<\/a>, do occur on these islands but are extremely rare. The majority of eruptions in Hawai\u02bbi are Hawaiian-type eruptions<\/a> because basaltic magma<\/strong> is relatively fluid compared with magmas typically involved in more explosive eruptions, such as the andesitic magmas that produce some of the spectacular and dangerous eruptions around the margins of the Pacific basin.<\/p>\n

Eruptions from the Hawaii hotspot<\/a> left a trail of underwater mountains across the Pacific over millions of years, called the Emperor Seamounts<\/a><\/p>\n

Hawai\u02bbi island (the Big Island) is the biggest and youngest island in the chain, built from five volcanoes. Mauna Loa<\/a>, comprising over half of the Big Island, is the largest shield volcano<\/a> on the Earth. The measurement from sea level to summit is more than 2.5 miles (4 km), from sea level to sea floor about 3.1 miles (5 km).<\/p>\n","protected":false},"excerpt":{"rendered":"

En 2011 publiqu\u00e9 un art\u00edculo sobre la edafogeograf\u00eda insular en que entre otros archipi\u00e9lagos se analizaba el de Haw\u00e1i. Hace unos meses le\u00ed\u00a0una nota de prensa que hac\u00eda referencia a otro \u201cpaper\u201d cuyo t\u00edtulo me pareci\u00f3 sugestivo. \u00a0Sin embargo, ha resultado ser una trampa (mucho tiempo gastado en vano). Es decir, su contenido es interesante y sorpr\u00e9ndete, por lo que poco os puedo decir al respecto, tras analizar la bibliograf\u00eda. Mis lecturas sobre el ciclo de vida de los sistemas insulares sobre puntos calientes del manto terrestre hac\u00edan \u00e9nfasis en que la desaparici\u00f3n de las islas se deb\u00eda m\u00e1s al\u2026<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[618,607,617],"tags":[20063,46714,20062,20061],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/143502"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/comments?post=143502"}],"version-history":[{"count":8,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/143502\/revisions"}],"predecessor-version":[{"id":144654,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/143502\/revisions\/144654"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=143502"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=143502"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=143502"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}