Techtonics Flashcards
(26 cards)
What is Alfred Wegener’s theory?
Continental Drift
What is Alfred Wegener’s theory on continental drift?
That the continents have moved and possibly still moving.
What is the evidence to continental drift?
- Some continents such as South America and Africa look like they could fit together like jigsaw pieces.
- The same fossils are found on each continent in bands which would match up if they were stuck together.
- Matching rock types (and ages) in the continents which he thought had been joined.
Why was continental drift rejected?
Because Alfred Wegener had no plausible reason why the continents had moved/drifted.
What is Harry Hess’ theory?
Sea Floor Spreading
What is Harry Hess’ theory on sea floor spreading?
He studied the oceans floor and realized they were growing outwards from mid-ocean ridges (which are undersea volcanoes).
What is the evidence of sea floor spreading?
- The nearer to the ridge, the younger the rock, this suggests the rock is made at the ridge.
- The sea floor is thickest near the continents, and thin near the mid-ocean ridge. This fits with the idea that the sea floor is growing from the ridge, as the older floor has more time for sediments to build up and form sedimentary rock.
- Magnetic striping: sometime the earths magnetic field swaps. This can be measured in rocks, as they show the direction of the poles when the rock forms (this causes magnetic stripes on the sea floor). The stripes are symmetrical around the ocean ridges, which can only be explained by new sea floor spreading out from the ridge in both directions.
What are the benefits and limitations of using models in science?
Benefits: Models are able to create either a blown up or shrunken version of something. It makes it easier for people to understand things that are either too small for us to see or to large that we can’t comprehend. Models allow us to view and understand concepts that are hard to describe and see.
Limitations: Models can create false interpretations of a concept. They are usually simplified which means they miss important features which leads to misunderstanding. Models are usually static/still, whereas, most scientific processes change over time.
What are plate tectonics?
The earths crust is broken into a series of pieces called ‘Plates’. These plates are moving (which leads to the movement of continents).
How is the movement of plates measured?
We can measure plate movement using GPS and radiometric dating which measures the rate of decay using radioactive isotopes.
How do Plates move in relation to the mantle?
The convection currents in the mantle cause the plates to be dragged and pushed with the convection currents.
What are the three different types of plate interactions /plate boundaries?
- Divergent (away)
- Convergent (towards)
- Transform (slide)
What happens at Divergent boundaries?
The two plates are pulling away from each other creating mid ocean ridges under the sea, rift valleys on land, new rock, volcanoes and some earthquakes. Mid Atlantic Ridge
What happens at Convergent boundaries?
There are three types of convergent boundaries:
1. Oceanic and Continental:
oceanic plate goes under the continental plate because it is more dense (subduction zone). This creates a deep ocean trench, and volcanoes and earthquakes on the continental edge.
Pacific Side Of South America.
2. Oceanic and Oceanic:
The fastest moving plate moves under the other one to create a subduction zone. Volcanic island chains form as do deep sea trenches and earthquakes.
Mariana Islands and Mariana Trench
3. Continental and Continental
causes huge fold mountains which are pushed up, these areas are likely to have huge earthquakes.
The Himalayas (due to Indian and Asian plates)
What happens at Transform boundaries?
Transform boundaries are where to plates slide against each other, building up friction. This means a lot of earthquakes are produced here but no volcanoes or mountains. San Andreas Fault, California
What is the Focus and Epicenter?
Focus: Where the earthquake originates (usually underground)
Epicenter: Directly above the focus on land.
What is the cause of Earthquakes?
A rapid release of energy as the tectonic plates move, friction between the plates must be overcome before they can move.
What are the different types of earthquake waves?
P-waves (primary)
S-waves (secondary)
Surface waves
Difference between the three types of waves?
P-waves are the fastest waves, Longitudinal, and the least destructive. (always arrive first)
S-waves are slower than p-waves, transverse, and are more destructive than p-waves (always arrive second)
Surface waves are the slowest, both longitudinal and transverse and are the most destructive wave. (always arrive last)
What measures earthquakes and there magnitude?
A Seismometer and is measured on the Richter scale.
How are the waves useful in measuring where the epicenter is?
The difference between the arrival of the p-waves and the s-waves can determine the earthquake is. Many seismometers can pinpoint the exact location of the epicenter.
How are volcanoes different from diverging and converging boundaries and hotspots?
If they are formed by a plate boundary, they are in the same spot and will always be active until the plates release all the pressure. Volcanoes that are formed on hotspots are usually apart of a chain and will one day become dormant when it moves off the hot spot.
How are Tsunami’s caused?
Tsunami’s are made from an earthquake out in the ocean which causes the waves to differ, the wave grows as the flow become more shallow.
How can you detect an Earthquake?
Siesmometers.
