Big Island of Hawaii: Geologic Field Assignment

Joseph Ouellette GEL 103 Summer 2011

Timeline of Hawaii The Hawaiian Islands were

created less than 10 Million ago by a hot spot near the boundary of the Pacific tectonic plate.

The oldest island, Ni’ihau, was formed during the Neogene period around the Philocene epoch, roughly 5.2 million years ago.

The Big Island, is the youngest of the islands. It was formed during the Pleisotocene epoch in the Neogene period, roughly 500,000 years ago. (Blay & Siemers, 1997)

Image Source: polynesian.com

Image source: hawaii-guide.com/bigisland

Hawaiian Hot Spot

A hot spot is a location in the earth’s mantle which is hotter than the mantle that surrounds it. Hot spots are usually found on or near the boundaries of tectonic plates. (wikipedia.org, 2011)

Hot spots, unlike tectonic plates, do not shift or move. Therefore they are constantly creating new volcanic island chains.

It is thought that the hotspot off the eastern coast of the Big island may have been active for 80 million years (Blay & Siemers, 1998)

Image source: http://en.wikipedia.org/wiki/Hotspot_(geology)

Big Island Volcanoes All of the volcanoes on the Big Island

are made up of igenous tholeiitic basalt as well as coarse grained gabbro and diabase.

The Big Island has a total of five volcanoes, of which three are still considered active; Kilauea, Mauna Loa, and Hualalai.

Kilauea during the same time as the island itself, having its first eruptions between 300,000 and 600,000 years ago. (USGS, 2011)

Kilauea first above ground eruptions occurred between 50,000-100,000 years ago. However the oldest dated rocks are around 27,000 years old. (USGS, 2011)

Kilauea is the most active of all the volcanoes, having erupted as recently as 1983. In fact it took until 2004 for the lava from this eruption to reach the ocean. (timelines.ws, 2011)

As of 2011, a new vent has opened in Kilauea causing lava to burst forth as high as 65ft in the air. (USGS, 2011)

The Big Island is one of the best locations to see rapid evolution.

Halemaumau Crater, part of the Kilauea Volcano: Ouellette 2011

Lava Rock

Lava when cooled forms an igneous rock, very porous and rough.

The lava rock on the Big Island is cooled Mafic lava which is low in Aluminum and silica levels. (wikipedia.org, 2011)

Lava when in a molten reaches temperatures between 700C and 1200C, and is 100,000 times more viscous than water.

Lava Rock Layers Lava on the Big Island of

Hawaii naturally moves from the cone of the volcano toward the ocean. Once the lava reaches the water’s edge it steams and hardens into lava rock.

Lava rock like other rock follows the Principle of Superposition, meaning the oldest layers are on the bottom and the youngest on the top.

Over time the layers of lava change through the erosion of the tide and change composition until they are sedimentary rock not igneous.

Sedimentary Lava Rock

Constant erosion causes lava rock to break apart and reform into sedimentary rocks throughout the Big Island.

These sedimentary rocks are often more smooth in texture and are not as porous due to surface erosion.

Sedimentary rocks in Hawaii are mostly found near constant running water or what had been constant running water.

Hibiscus Flower

Most pollinating plants developed in stages from oceanic spores.

The hibiscus flower of Hawaii contain two indigenous species and five developed over time through pollination, through two separate independent colonizations on the the islands. (wikipedia.org, 2011)

The Hibiscus arnottianus is considered to be native to the Hawaiian Islands.

Hibiscus amottianus

White Hibiscus: Ouellette 2011

Banana Tree

The banana is a large herbaceous flowering plant, which generally grows between 9-11ft tall.

Bananas were first recorded being cultivated in South East Asia around 8000 BCE.

It is believed that the spread of bananas to Hawaii came with the early settlers from the Marquesas Islands between 500-700 AD. (Kauai Railway Plantation, 2011)

In Hawaii there are six different variety of banana, the two most common are the Brazillian and Cavendish. (Wright, 2011)

Family: Musaceae Genus: Musa

Musa manzano “Apple Banana”: Ouellette 2011

References Blay, R. & Siemers, R. Kaua’i’s Geologic History (1997) Retrieved on July17, 2011. From:

http://www.hawaii.edu/environment/ainakumuwai/html/ainakumuwaiislandformation.htm

 Kauai Plantation Railway. Retrieved July 16, 2011. From: http://www.kauaiplantationrailway.com/aghawaii.htm

Timelines. Retrieved July 21, 2011. From: http://timelines.ws/states/HAWAII.HTML

United States Geological Service. Hawaii Volcano Observatory: Kilauea. Retrieved July 20, 2011. From: http://hvo.wr.usgs.gov/kilauea/

Wright, M. G. Crop Knowledge Master: University of Hawaii Manoa Extension. Retrieved on July 18, 2011. From: http://www.extento.hawaii.edu/kbase/crop/crops/i_banana.htm#top

Wikipedia.org. Lava. Retrieved July 13, 2011. From: http://en.wikipedia.org/wiki/Lava

Wikipedia.org. Hibiscus. Retrieved July15, 2011. From: http://en.wikipedia.org/wiki/Hawaiian_hibiscus 

Wikipedia.org. Hot spots. Retrieved July 17, 2011. From: http://en.wikipedia.org/wiki/Hotspot_(geology)