QUICK QUIZ 1.Give an example of an Continental Island 2.Name one of the three parts of a Ridge. 3.An area of Subduction will form what type of structure in the ocean? 4.What is a flat topped Seamount called? 5.Long Island and England are what type of Islands?
Island Formation How do Islands form? Island Arcs- Philippines Hot spots---The Hawaiian Islands What does Darwin have to do with this? Atolls and Coral reefs
1. Continental Islands = UK, New Zealand. 2. Island arcs – Philippine & Aleutian Islands 3. Volcanic Islands- a. volcanic = Iceland, Hawaii, Azores, etc. (1) along mid-ocean ridges, or (2) mid-basin “hot spots”. b. coral - atolls (1) formed in warm, clear, tropical oceanic waters. (2) have volcanic bases.
Continental Islands Large chuck of land breaks off of a continental land mass. Ireland, England were originally part of the European continent (fig 2.14 p 31) New Zealand was part of Australia
Which Island can the Mid Atlantic Ridge be seen on land. 1.Ireland 2.Iceland 3.Finland 4.Greenland 5.It cannot be seen on land
The three part of a ridge are the 1.Flank, Ridge and slope 2.Flank, Ridge Valley and Base 3.Flank, Rift Valley and Crest 4.Slope, Break and Shelf
An example of Island Arcs created through subduction are 1.Iceland 2.Hawaiian Islands 3.Manhattan Island 4.The Islands of Japan
The most common geological structure in the ocean is 1.Abyssal Plains 2.Seamounts 3.Guyots 4.Abyssal Hills
Oceanic Crust – Continental Crust
B. Island Arcs 1. arc-shaped chains of islands (Marianas, Aleutians) 2. usually on continent side of trenches. 3. made by active volcanoes - explosive type. 4. marginal basins a. between arcs and continents b. serve to trap sediment and block it from the deep sea. Aleutian Islands
Island Arc Formation
Hot Spots-Volcanic Islands A volcanic “plume” at a fixed spot in the mantle pushes through the crust creating a volcano. The volcano builds becoming a seamount which crests the ocean surface. The crust moves over the spot and the process is repeated. This is why you will get Island Chains such as the Hawaiian Islands
Hot Spot Formation
Volcanic Features The Island Of Hawaii
Coral Reefs Tropical waters only (temperature matters) 20 – 30 degrees C Form in shallow water next to island As island erodes, reef remains Can only live in Photic zone- If the Island (Atoll) sinks below the photic zone the coral will die. Photic Zone is the upper layer of water where light can penetrate.
Largest reef –Great Barrier Reef covers 80,000 square miles
Charles Darwin
Darwin In his voyage around the world in the 1830’s Darwin formulated his theory on reef and atoll formation This theory is still considered valid and is used to this day
Life of a coral reef (as per Darwin) Fringing reef Barrier reef Atoll