P1.2 What do we know about the Earth and how it is changing?

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  • Created by: sofsdvds
  • Created on: 21-04-16 18:07
What provides evidence for changes in the Earth?
Rocks - erosion, sedimentation, fossils and folding
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Why are continents not worn down to sea level by erosion?
Mountains are continuously being formed
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What can rock processes seen today account for?
Past changes
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What is the age of the Earth and how can it be estimated?
The age of the Earth can be estimated from, and must be greater than, the age of its oldest rocks, which are about four thousand million years old
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What was Wegener's theory?
Wegener’s theory of continental drift - 300 million of years ago there just used to be one supercontinent but then the continents have drifted apart
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What is the evidence for Wegener's theory?
Coastlines of Africa and South America continents fit together with their matching fossils and rock layers
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What does Wegener’s theory account for?
Mountain building
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Why was Wegener’s theory rejected by geologists of his time?
1. Movement of continents not detectable, 2. too big an idea from limited evidence, 3. simpler explanations of the same evidence, 4. Wegener an outsider to the community of geologists
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What is seafloor spreading?
Seafloor spreading - when the magma rises up (due heating from the core of the Earth causing convection currents) through the seafloor, solidifies and forms underwater mountains
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What is the rate of seafloor spreading?
A few centimetres a year
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Explain the pattern in the magnetisation of seafloor rocks on either side of the oceanic ridges
As liquid magma rises up out of the gap, iron particles in the magma align themselves with the Earth's magnetic field and are set as the magma cools to form rocks. Every half a million years the Earth's magnetic field swaps direction
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What generally occurs at the edges of tectonic plates?
Earthquakes, volcanoes and mountain building
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What does movement of tectonic plates cause?
Earthquakes, volcanoes and mountain building, and contributes to the rock cycle
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How do earthquakes happen?
If plates get stuck when sliding past each other and the pressure builds up until it is too high and suddenly one of the plates move
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How do volcanoes form?
Where an oceanic plate is forced under a a continental plate causing the continental plate to rise up and magma is forced up it
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How do mountains form?
Where two plates collide and are force rock upwards
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What do earthquakes produce?
Wave motions on the surface and inside the Earth
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How are Earthquakes detected?
Detected by instruments called seismographs located on the Earth’s surface
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What 2 types of waves do earthquakes produce?
P-waves and S-waves
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What type of waves are P-waves and S-waves?
P-waves are longitudinal waves and S-waves are transverse waves
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What can P-waves and S-waves travel through?
P-waves travel through solids and liquids and S-waves travel through solids but not liquids
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What is a transverse wave?
The vibrations are at 90 degrees to the direction of travel of the wave
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What is a longitudinal wave?
The vibrations are along the same direction as the wave is travelling
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Which travels faster P-waves or S-waves?
P-waves travel faster than S-waves
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What is the wave equation?
Distance (m) = wave speed ( m/s) × time ( s)
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What is the structure of the Earth working from the centre outwards?
Solid inner core, liquid outer core, mantle and crust
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What is a wave?
A wave is a disturbance, caused by a vibrating source, that transfers energy in the direction that the wave travels, without transferring matter
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What is the frequency of waves?
The number of waves each second that are made by the source, or that pass through any particular point (measured in hertz (Hz)),
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What is the wavelength of waves?
The distance between the corresponding points on two adjacent cycles
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What is the amplitude of a wave?
The distance from the maximum displacement to the undisturbed position
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What is the wave speed equation?
wave speed (m/s) = frequency (hertz, Hz) × wavelength (m)
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What is needed for a constant wave speed?
The wavelength of the wave is inversely proportional to the frequency.
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Other cards in this set

Card 2


Why are continents not worn down to sea level by erosion?


Mountains are continuously being formed

Card 3


What can rock processes seen today account for?


Preview of the front of card 3

Card 4


What is the age of the Earth and how can it be estimated?


Preview of the front of card 4

Card 5


What was Wegener's theory?


Preview of the front of card 5
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