Dr. Sidney White: Advisor

Ohio State University THE MANY FACES OF MADAM PELE Senior Thesis BY GERALD A. DERRYSHIRE Submitted in partial fulfillment of the requirements leading to a Bachelor of Science degree in GEOLOGY Dr. Sidney White: Advisor Winter Quarter 1970 SLIDE 1 Madam Pele, so called by the natives in a mixture of res- pect and faailiarity, is described as a revengeflll ~~oddess, taking care of her friends and destroying her enenies. The legend of this fire goddess revolves around her search for a hone, visiting first one island and then another. Her search is preserved in the crumbling remains of extinct volcanoes, her destination revealed by the fiery eruptions of Kilauea. Many residents in the vicinity of her home . will testify that they have seen her in the form of an old woman prior to her display of awesome fury along Kilauea's flanks; however, when her activity is confined to the crater itself, she is described as a youthful woman of great beauty. The accounts of this myth provide the legendary foundation of the Hawaiian Islands and these islands reflect..."The ?any Faces of Madam Pele". SLIDE 2 THE EL4NY FACES OF MADAM PELE Photography and Story by Gerald A. Derbyshire 1970 SLIDE 3 The Hawaiian Islands are a chain of shield-shaped basaltic domes built over a fissure 1600 miles long in the ocean floor. Tiny dots in the isolation of the central Pacific, the islands are actually the tops of these shield-shaped domes, which, perhaps, constitute the greatest mountain -1- range on earth, built up from the ocean floor by thousands upon thousands of volcanic lava flows with an average thick- ness of ten feet. The average depth of the floor of the ocean around the island chain is about 15,000 feet. There- fore, the lowest of the islands are mountains nore than 15,000 feet high and Wauna Kea, on the island of Hawaii, rises more than 30,000 feet above its base. It is the highest peak on the islands, and the world's highest mountain in terms of elevation above its base. SLIDE 4 The volcanoes began their history above sea level during the late Tertiary, approximately ten million years ago. Moat of them became dormant either before or during the early Pleistocene; however, activity was renewed in the late Pleistocene. Even though only a few miles apart, each volcano in the Hawaiian Islands was built seemingly from an independent magma reservoir; each has an erosional history particular to it8 height and form; and each differs some- what in age from the others. SLIDE 5 The volcanoes seem to have developed from the fissure in a northwest to southeasterly direction across the floor of the Pacific. The relative age of the islands is indicated by the extent to which they have been destroyed by erosion. SLIDE 6 Extending northwestward from Niihau are 26 reefs and shoals which mark the summits of submarine volcanoes, known as the Leeward Islands. These northweeternmost volcanic inountaina - 3 - have been eroded away until no more volcanic rock may be seen. The visible parts of Ocean and Midway Islands are forned entirely of oraanic limestone and calcareous sand, but at a depth of only a few hundred feet the limestone reefs rest on the truncated summits of great volcanic noun- tains. SLIDE 7 The islands of Rauai and Oahu were deeply eroded by streams and waves before a recurrence of volcanic activity buried much of their lowlands beneath layers of later lava flows. SLIDE 8 On Maul, the volcanic mountain cornpriaing the western part of the island has been deeply dissected by streams, with the formation of huge valleys such as Iao. SLIDE 9 Halsakala Volcano, forming the eastern part of Maul, also had great valleys cut into it by stream erosion before renewed volcanisn partially filled the work of the streams. SLIDE 10 Hawaii is the southernost and largest of the islands and also the youngest. Of the five volcanoes that built this largest of deep sea islands' (4,021 square miles), Kohala Volcano at the northern end of the island is the oldest. SLIDE 11 Mauna Kea has not been active since the arrival of the Hawaiian people, but has erupted since its summit was covered by a small glacier during the Pleistocene Epoch about 15,000 years ago. SLIDE 12 Hualalai, on the western side of the island, has erupted once in historic time, during 1800-1801. SLIDE 13 The two southernmost volcanoes, Mauna Loa and Xilauea, are still quite active and almost completely untouched by the forces of erosion. SLIDE 14 The molten rock expelled by the valcanoes in reality is not a simple melt, but a complex solution of silicates and oxides. It appears always to contain volatiles, either dis- solved in it or simply enclosed in it as bubbles. Also, the molten rock often contains solid crystals of various miner- als, which have precipitated from the solution through a process of "fractional crystallization". This hot liquid is called magma. While the magma is confined under sufficient pressure, the gaseous constituents remain in solution; but, as the magma rises toward the surface and the overlying pressure is reduced, the gases escape, sometimes with ex- plosive violence. When this magma is poured out onto the earth's surface it is referred to as lava. SLIDE 15 Lavaa vary greatly in composition. The composition affects the viscosity, thereby influencing the ease with which the gasea are liberated, and as a consequence determines the type of eruption, the rate of flow and other characteristics. When considering only the chemical elements in a solid state, the substances present are usually expressed as oxides of the various elements which the lava contains, The most abundant oxide in lavas is silica. In general, as the per- centage of silica increases so does that of the alkalies, and as it decreases there is an increase in the percenta~e of iron, magnesia and lime. The majority of Hawaiian lavas are nezr the silica-poor end of the scale and are relatively rich in iron, lime and magnesia.. SLIDE 16 The most coamon lava of all the Hawaiian volcanoes is the type known as olivine basalt. Its nost abundant constituent is a light-colored variety of plagloclase feldspar called labradorite. It generally comprises nearly half of the crystallized rock. SLIDE 17 The olivine basalt grades into rocks known as andesite, richer in silica and alkalies than the basalts and generally lighter in color. Andesite is not present at Kilauea and Mauna Loa, but is abundant in Nauna Kea and Haleakala on the island of Maui, SLIDE 18 There are two principal types of lava flows produced by Hawaiian volcanoes, Pahoehoe flows occur when lava con- taining much entrapped gas spreads out in thin sheets. The surface of pahoehoe lava Is smooth and billowy and frequently molded into coiled, rope-like masses. SLIDE 19 Such billowy surfaces commonly develop in basaltic lava, on which a skin-like surface coivers the liquid lava below, and as the flow contlnuee to move' the smooth skin is wrinkled into ropey surfaces which are preserved on the perimeter of the pahoehoe flow when the mass finally solidifies. SLIDE 20 The skin which develops on the cooling lava may further solidify forming a crust. SLIDE 21 This crust may eventually develop a more or less contin- uous roof, and the lava stream commences to flow within a tube of its own making. At the end of an eruption, most of the inolten lava may drain out of the tube leaving an open tunnel commonly as much as ten to twenty feet in diameter with an arched roof and a nearly flat floor. The floor is the final solidified surface of the lava stream which flowed through the tube. Such features are common in many pahoehoe lava flows and are referred to as lava tubes. SLIDE 22 Aa lava flows, on the other hand, typically display a jag- ged or more blocky surface, as illustrated by this flow along the northeast rift zone of Mauna Loa; the summit of Mauna Kea towers in the background. The lava is generally void of gases and the vesicles, or bubbles created by the trapped volatiles contained within the magma, are replaced with air. The loss of these volatiles is responsible for the more rapid cooling and greater viscosity of this type of lava. SLIDE 23 The fresh flows of aa lava extending downslope appear black. The fresh pahoehoe flow8 may a180 appear black, but when -7- light is reflected fron them they appear silvery gray from a dist~nce,Older lavas are dark gray and still older ones reddish-brown, The reddish-brown color is a result of the advanced stage of oxidation of the iron contained in the lava. SLIDE 24 Despite their differences in physical appearance and nature of flow, chenical analyses of solidified fragments of the two types of lava from the same flow show them to be essen- tially identical in chemical conposition which suggests that rivers of pahoehoe may pour from volcanic vents or fis- sures, but as it flows downslope it loses its volatiles and consequently increases its viscosity and the lava eventu- .ally changes to aa. An aa lava flow from the 1950 eruption of Mauna Loa is shown here crossing highway 11 along the volcano's southwest flank, SLIDE 25 Where aa lava flows into the sea the contact of the hot lava with sea water causes steam explosions that throw up droplets and fragments of the hot lava, The droplets of still molten lava are quickly solidified to a black or dark brown glass.

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