- The oceans cover about 2/3 of the earth’s surface. Asia Pacific encompass Pacific Ocean, the largest of the oceans as well as Indian Ocean.
- The project has developed a spatial data browser Global Mapper (for details, refer to “From Local to Global: Spatial Data Browser”, Part 2 of the report Contents Modules and Interactive Multimedia Browser, submitted to the UNU/IAS in March 2005; also see “Global Mapping Software” to be submitted to the UNU/IAS in March 2006.
- The browser combines spatial data coming from (i) IKONOS (1 meter resolution), (ii) LANDSAT (10 meter resolution), (iii) NASA and NGA GTOPO (1 arc second = 30 meters; we use 100 meter resolution data here), and Global Digital Elevation Model bathymetry ETOPO (2 minute by 2 minute). For a global analysis, the third group of data which combines GTOPO (land) and ETOPO (ocean) data is suitable.
- Plate-tectonics theory is introduced which explains the dynamics of divergent plate boundaries with mid-ocean ridges and convergent plate boundaries with trenches created by oceanic crust submerging under continental crust, and resultant volcanic arcs.
Course Outline:
2010-01-22
Digital maps and 3D
- Digital maps for the entire Asia Pacific, Hawaii, Fiji and the vicinity (Samoa, Tonga, Vanuatu, New Caledonia), New Zealand, Japan, and part of Indonesia are shown.
- This is accompanied by three-dimensional views of the region, which clearly show:
- Hawaiian Islands extending all the way to Midway;
- New Zealand, Fiji, Samoa, Vanuatu, and New Caledonia are linked by chains of islands and trench;
- Ocean trenches extend to the west, passing New Guinea, the Philippines, Taiwan, Okinawa and the mainland Japan.
- String of small islands extends from Japan to the Pacific.
- Turning to Indo-Australian plate, trench is clearly visible which runs along Indonesia where devastating earthquake occurred affecting the entire coasts of the Indian Ocean.
Hot Spot
- But what about Hawaii? One look at the map shows us that the Hawaiian Islands are not located near the edige of any plates. Instead, Hawaii’s volcanoes are located in the center of the vast Pacific plate.
- The hot spot theory explains how this can be so … A hot spot is the source of the Hawaiian Island. … The hot spot continues to build the islands larger — until the Pacific plate, constantly moving toward the northwest at the speed of about four inches per year, carries the island off the hot spot. Then, a new volcano begins to from over the hot spot.
- Over a time-span of nearly 70 million yers, a hot spot within the earth has produced the 3,500 mile long Emperor Seamount-Hawaiian Island chain.
- Kaua’i: almost 6 million years old
- O’ahu: almost 4 million years old
- Moloka’i: almost 2 million years old
- Lana’i: about 1.5 million years old
- West Maui: about 1.5 millon years old, East Maui: almost 1 million years old
- Hawaii: about ahlt a million years old and still growing
- Loihi: may become an island in about 60,000 years
In the Northwestern Hawaiian Islands, Nihoa and Necker still show remains of the original volcanic mountain. Further northwest, French Frigate Shoals has almost become a coral atoll. And further Still, Maro Reef, Midway, and Kure are among several atolls that make up the last of the Hawaiian Island chain.
Source: Orr and Cook, Discover Hawaii’s Birth by Fire Volcanoes
Coral Atolls and Guyots
- Corals settle and grow on the slopes of the new volcanic island. At first the coral reef is near shore.
- As the volcanic island erodes and the sea floor slowly sinks, the distance between the shore and the coral reef increases. If the sea floor sinks slowly enough, the coral reef keeps growing near the surface. (In Hawai’I, coral reef grow upward at a rate less than an inch a year.)
- Eventually, the volcanic island disappears beneath the surface of the sea and becomes covered over by coral and sand. The island is now an atoll.
- If the sea floor sinks too quickly, or as the Pacific plate moves atoll into the colder water, the coral reef dies and the atoll is washed away by wind and waves.. Only a guyot remains.
Source: Orr and Cook, Discover Hawai’I’s Birth by Fire Volcanoes
Sea Level Change and the Southwest Pacific
- 18,000 years ago, sea level in this region (southwest Pacific) was some 120-150 m lower than it is today. Islands were much larger. Many islands existed which are now below sea level. (Nunn, Oceanic Islands)
- Sea level rise has caused islands to disappear or become smaller and further apart. Late Quaternary sea-level rise had important consequences for island environments and for the movements of humans and others throughout the region… (ibid)
References:
- Patrick D. Nunn, Oceanic Islands, Blackwell, 1994.
- Katherine Orr and Mauliola Cook, Discover Hawai’I’s Birth by Fire Volcanoes, Island Heritage, 2004.
- Glen Coates, The Rise and Fall of the Southern Alps, Canterbury University Press, 2002.
- Karen Williams, Volcanoes of the South Wind, A Field Guide to the Volcanoes and Landscape of Tongriro National Park, Tongariro Natural History Society, Inc., 2001 edition.