Oceanography 2 Flashcards
What plate boundary is spreading?
Divergent
What is filled into the spaces left at a divergent boundary?
New crust
What boundary are most mid ocean ridges located at?
Divergent
What is a mid ocean ridge?
Giant undersea mountain range
Why does a mid ocean ridge sit on top of the mantle?
The new crust is warmer than surrounding crust and has lower density, it sits on top of the mantle creating the mountain chain.
What is a rift valley?
Valley that runs along middle of mid ocean ridge
What type of crust forms at divergent boundaries?
Oceanic
What type of rock is oceanic crust?
Igneous
Where on the mid ocean ridge is crust the youngest?
At the spreading center (the valley) and gets older the farther from the boundary
Why is sediment thin or non existent in ocean ridge areas?
Because it’s younger and has not had time to accumulate
What type of convection is found at mid ocean ridges and why?
Upwards convection because the heat rate is higher
What creates a mid ocean ridge?
Magma rises from partial melting of the mantle as the plates spread
What is a convergent boundary?
Two plates moving towards each other.
What happens at an ocean-ocean convergent boundary?
One plate is subducted. Often the colder and older plate foes under.
What happens at an ocean-continent convergent boundary?
The denser oceanic plate will subduct
What happens at a continent-continent convergent boundary?
Collision and deformation of pre existing continental rock. This pushes the rock up forming mountains.
What geological feature is found at continent-continent plate boundaries?
Mountains
What is a transform plate boundary?
One plate sliding past another
What is a transform fault?
A strike-slip fault at a transforming boundary. Occurs between sections of tectonic plates. Connects mid ocean ridges.
What is common along transform faults?
Earthquakes
What causes an earthquake?
The shaking caused by rupture and displacement of rock beneath the earths surface. Basically a rock becoming stuck on another rock and then the pressure builds and is suddenly released and releases a massiv amount of energy.
How do earthquakes happen?
1: the rock under stress becomes deformed
2: when it can no longer stand the deformation, it breaks down and two sides slide past each other
What determines the magnitude of an earthquake?
The extent of the area that breaks and average amount of sliding
Where on divergent plate boundaries are earthquakes popular?
A narrow zone close to the mid ocean ridges.
Are earthquakes abundant on subduction zones?
Yes
Where do most earthquakes occur?
Along transform faults
Are earthquakes on divergent and transform boundaries shallow or deep? Why?
Shallow, the crust is not very thick.
What causes earthquakes at convergent plate boundaries?
The motion of the subduction
Why are earthquakes popular at faults?
Because faults is where rock moves pst rock and most faults are found at the boundary of plates.
What are seamounts?
Under water volcanoes
What does a seamount turn into if it breaks the surface of the ocean?
A volcanic island
Where can seamounts occur?
Divergent boundaries from magma rising, can result in seamount chain. Ocean-ocean subduction zones from rising magma.
What are tablemounts/guyots:
A flat topped seamount where the top is flattened down by erosion
What is a mantle plume?
“Hot spot” where mantle material (hot) rises in a plume and affects the overlaying crust.
What can a mantle plume cause?
Volcanoes to erupt because it melts lithosphere and surrounding mantle to form magma that rises.
What’s an example of a mantle plume on the continents?
Yellowstone
Do mantle plumes occur mostly in the ocean or continent?
Ocean
What are hydrothermal vents?
Jets of super heated water in deep ocean
Where do hydrothermal vents come up from?
Cracks in the crust
What’s the average temp of hydrothermal vents and what’s the average temp of regular water at that depth?
350 degrees Celsius (average is 2-4 Celsius)
What does a hydrothermal vent look like in the water?
A cloud of thick black smoke
How are hydrothermal vent created?
1: water percolates into crust where plumes of magma are close to surface.
2: water germs super heated by magma
3: moves back to surface through convection and is released through the cracks
Why is the water black near hydrothermal vents?
Because the hot water is dissolving minerals from surrounding rock, they precipitate out as small particles which turn the water black.
What geological feature is presentiave of a large chimney of black water?
Hydrothermal vents
Where is a popular place for hydrothermal vents to pop up?
Along oceanic ridges where there is shallow crust and a lot of tectonic activity or near volcanic activity.
How does a hydrothermal vent support life?
Water exiting the vent is rich in hydrogen sulfide and oxygen. Bacteria use chemosynthesis to turn the energy from the oxidizing sulfide compounds into carbs from Co2 and water. These bacteria them are the base of the food chain. They get eaten and the animals that eat them survive off of the bacteria in their tissue.
What is chemosynthesis?
The process of turning energy from oxidizing sulfur compounds into carbs. It’s the reduction of hydrogen sulfide by bacteria.
Describe how mantle convection works.
Circular system of rising and sinking water by density. Pot of water on the stove, bottom of pot near heat source becomes hot and expands and then is less dense, less dense water rises and the cooler more dense water sinks then gets heated and rises, this creates a pattern of rising and sinking.
How does mantle convection cause tectonic plates to move?
The horizontal movement of the mantle under the crust drapes the plates with them. Convection currents in the mantle go upwards, new lithosphere forms and the plates move apart. Convergent plates have downwards convection and is pulling the plates into each other until subduction occurs.
Describe the Big Bang theory
The universe violently blinking into existence
When did the Big Bang happen?
13.77 bya
What were the steps of the big band?
1: the universe was hot and dense and had only a small amount of very small particles. Smaller than an atom.
2: it began to cool, particles began colliding and sticking together.
3: early collisions produced hydrogen and helium and small amounts o lithium.
4: gravity began to cause clouds of early elements to coalesce into stars, inside stars is where heavier elements were formed.
When was the solar system created?
5 bya
Why do stars shine?
Full of heat and pressure whcih cause smaller atoms to clash together and become larger atoms. Large amounts of energy are released when some atoms fuse. The energy is the shine.
What are the three categories of planets? ```
Terrestrial, Jovian (gas giants), ice giants
What did the solar system start as? Describe it?
A nebula: cloud of dust and gas
How did the solar system form?
Static or gravity cause patch of nebula to collapse in on itself.
What is the remaining dust and gas leftover from nebula formation called? Describe the shape.
A protoplanetary disk, flattened disk of gas and dust that rotates around the star.
What is accretion? List the steps
The concept that forms planets/stars.
1: static electricty lumps minerals and rock together
2: lump browns bigger’3: gravity takes hold and pulls things that are farther away in and grows it even more
4: eventually becomes large enough that gravity is strong enough to hold onto gas molecules.
What kind of elements are found in larger stars?
Heavier elements like iron and nickel
What does a star turn into when it dies? What happens?
A supernovae : casts off newly formed atoms into space
How did earth form?
Accretion, after many generations of stars creating heavier elements and casting them into space to make elements abundant enough fro planets like earth.
Describe terrestrial planets and list their names
Core of metal surrounded by rock: Earth, mercury, Venus, mars
Describe and name Jovian planets
Gas giants. Consist f hydrogen and helium: Jupiter and saturn
Describe ice giants and name them
Consist largel of water ice, methane ice, ammonia ice with rocky cores: Uranus and neptune
Whcih planets are closest to the sun?
Terrestrial planets
What planets are farthest from the sun?
Ice giants
