Flashcards in The Restless Earth Deck (47)
Describe the characteristics of the Earth's CORE:
7000 degrees, solid iron and nickel ball.
Describe the characteristics of the Earth's MANTLE:
Semi-molten rock, moves very slowly and has convection currents. Tectonic plates float on top of it.
Describe the characteristics of the Earth's CRUST:
20km thick, divided int plates. Two types of crust: continental and oceanic.
Why do the plates move?
There are convection currents in the mantle nderneath
Describe the characteristics of continental crust:
Made of granite, much older (up to 3.8 billion years old), less dense, not renewable, can't be destroyed, much thicker.
Describe the characteristics of oceanic crust:
Made of basalt, much younger (less then 200million years old) more dense, renewable, can be destroyed, much thinner.
Name at least 3 major tectonic plates
Name the 4 types of plate boundary:
Describe what happens at a Constructive plate margin:
2 plates move away from each other, leaving a gap for magma to rise up through.
Describe what happens at a Destructive plate margin:
Oceanic crust descends below less dense continental crust. It is melted due to friction, forming magma, which can then rise through holes in the continental plate and form volcanoes.
Describe what happens at a Conservative plate margin:
Two plates move past each other in a parallel motion.
Describe what happens at a Collision margin:
Two plates of the same density are pushed together. Because neither one can be subducted, they buckle and form fold mountains.
At which plate margin(s) will you find earthquakes?
All of them.
At which plate margin(s) will you find volcanoes?
Constructive and Destructive.
What are the 4 pieces of evidence for Wagner's continental drift theory?
At which 2 boundaries can fold mountains form?
Destructive and collision
Why can fossils of sea creatures sometimes be found at the summits of fold mountains?
If there is sea between two plates as they move together at a collision boundary, sediment from the sea floor can be pushed up when the two plates come together, and as they're compressed into sedimentary rock to form the fold mountains, fossils are also formed.
Name some human uses of fold mountains:
-Hydro electric power
What is the focus of an earthquake?
The point int he Earth's crust where the seismic waves originte
What is the epicentre of an earthquake?
The point on the Earth's surface directly above the focus, where the shock waves are strongest.
What are primary waves?
The first seismic waves to reach a seismograph, as they have the highest velocity.
What are secondary waves?
The seconds waves to reach a seismograph, they travel slower through rock.
What does the Richter scale measure?
The amount of energy released by an earthquake, using a seismometer.
What is the Richter's scale?
1-10 for magnitude, but there is no limit on how high it can go. It is a logarithmic scale.
What does the Richter scale tell you?
It is logarithmic, so a 6 is 10 times more powerful than a 5, and 100 times more powerful than a 4.
What does the Mercalli scale measure?
Th damage caused to an area by an earthquake.
What is the Mercalli's scale?
1-12, or I-XII as it is usually written in Roman numerals.
What does the Mercalli tell you abut an earthquake?
It uses subjective opinion, so different people have different opinions on where on the scale the earthquake is.
What are the advantages and disadvantages of the Richter scale?
-It is accurate, and results are produced by a machine
-Based on scientific fact, rather than opinion.
-Expensive, so not available to LEDCs
-Must be a seismograph in place to take a reading