1. Coral Reef and Volcanic Island Formation

2. How do volcanic islands form?
Many oceanic islands get formed as a result of underwater volcanic eruptions
Many islands found around boundaries of tectonic plates (but not all)
Areas of active plate tectonic movement and volcanic activity known as hot spots

3. Hotspot Theory
Hot spots are volcanic regions thought to be fed by underlying mantle significantly hotter compared to the surrounding mantle
Occurs where one of earth’s outer tectonic plates moves over a hot part of the mantle
Allows magma and lava to rise through the plates
Produce large volcanic eruptions
Also know as “mantle plumes”

5. Example of Hotspots: Hawaii
Hawaiian islands are good examples of volcanic islands found around hotspots
Hawaii was formed as a chain of seamounts
Each island or submerged seamount is successively older toward the northwest
Due to the northwest motion of the oceanic plate
Older seamounts were once above sea-level but went below as the oceanic plate began to sink

7. Geology of Coasts
The geology of coasts can vary depending on the terrain of the land
Some coasts are sandy; others are rocky
Beaches are formed as a result of loose sediments eroding from land
Waves, tides, and precipitation can erode rock on the shore

8. Beaches vs Rocky Coasts
Beaches are composed of sand (eroded rock), rock, and shell and bone fragments
Delta – a landform found at the mouth of a river, carrying sediments to an ocean shore
Topographically flat
Rocky coasts formation dates back to ice age as Earth warmed and carved valley where ocean filled
Fjord – a long, narrow inlet of the sea between high cliffs
Iceland, Norway, Chile
Topographically steep
Beaches
Rocky Coasts

11. Formation of Coral Reefs
Coral reefs form when free-swimming coral larvae attach to submerged rocks on the edges of islands or continents
Three different types of reefs:
Fringing
Barrier
Atoll

12. Formation of Coral Reefs
Fringing reefs – lie a few kilometers offshore and run parallel to the mainland
Water shallow on shore side; deep on ocean side
Florida Keys and Caribbean
Barrier reefs – lie 20 – 50 kilometers offshore and are separated from the island by a channel
Atoll – a string of coral islands that form a circle with a lagoon in the middle
Found in Pacific Ocean