Types of Reefs Flashcards
(21 cards)
What is volcanic arc?
Chain of volcanoes formed above subduction plate
Volcanic island arc is the result of ____ that forms island
Offshore volcanoes
Formation of volcanic island
Oceanic plate subduct beneath another plate and oceanic trench is formed. Since oceanic plate is covered with water it lowers the melting point (flux melting) . As the plate subduct it is exposed to greater pressure, this pressure squeezes out the water, hence, introducing the water to the mantle and forms magma. Magma roses and forms volcanic arc which will form volcanic island arc.
How does volcanic island arc formed?
Subduction of oceanic plate - formation of oceanic trenches - melting of mantle - formation of magma - magma ascends - formation of volcanic island arc
How does the water saturated oceanic plate affects the melting point?
It drastically lowers the melting point ; flux melting ; where it accounts most of the magma at subduction zone
Define hot spot
Volcanic locale that are hotter than surrounding mantle
What are the two theories in formation of hotspot?
- Thermal diaprism - mantle plumes forms a bulge (diapirs). Magma heats up the crust and forms a crack where magma makes its way up to the surface.
- Weak crust/ Thin crust - hotspots are not anomalously hot but rather the crust is thin or weak
Relate the origin of the formation, age, and characteristic of volcanic arc based on the distance from the hot spot
As hot spot are anomalously hot it can create volcano. It is believed that hot spot will stay still but rather huge plates move around. With this, the farther the volcano form the hot spot the older and inactive it gets.
What is hot spot tracks/chains?
These are the chain of volcanic islands, atolls, and seamounts.
Hawaiian Emperor Chain
Emperor seamounts - Koko Seamounts
Hawaiian Ridge - Midway Atoll
Hawaiian island - Maui, Hawaii, Loihi
What plate motion does island arc got carried away?
Pacific plate motion
Development of reef
Fringing - Barrier - Atolls
Youngest and most common reef
Fringing reef
Least diverse reef
Fringing reef
Other term of fringing reef
Shore reef
How does coral reef forms
Larvae settlement - polyp - secretion of CaCO3- formation of exoskeleton - substrate for more polyps - formation of coral reefs
What are the other organisms that contributes to the structure of the reef
Calcareous algae adds sediments and organisms with calcareous skeletons
Components of fringing reef?
Reef slope - closest to the ocean
Reef flat - widest part
Largest fringing reef
Ningaloo reef
Where is Nigalooo reef located?
East Indian Ocean ; west coast of Australia
Places where fringing reefs are found
African shore, Israel, Australia, and Kenya
