Week 3: Earth and its Interior Flashcards
How long ago did Earth form?
4.6 x 10^9 years ago (4,600,000,000 years ago)
What is the “Giant Impact Theory”?
The moon was created through a collision between Earth and Theia
Be able to discuss the three main layers of the rocks on the Earth’s crust.
-Core
Most dense part of the interior
-Mantle
Less dense than the core
-Crust
Least dense layer
What are the two most common types of rocks on the Earth’s crust? What types of crust do you find these rocks in?
Basalt (55% of Earth’s surface)
Found in oceanic crust
Granite (45% of Earth’s surface)
Found in continental crust
How large is the mantle compared to other layers of the earth?
Ranges from 35km to 2890km
Largest portion of the Earth’s interior
What is convection?
The transfer of thermal energy (heat) by the movement of fluid
What effect does the convection currents have on the crust of the earth?
Convergent - towards
Divergent - away
Transform - slide past
What are the main differences between the inner and outer core of the earth?
- The inner core is mostly solid iron and nickel due to extreme pressures
- The outer core is molten which means it is able to flow as a liquid
What is differentiation? If an object is differentiated (has layers), what does that imply about the object’s early history?
Differentiation is the process of denser materials separating out from lighter materials
This implies that the materials are free to move around
How do you measure the age of the planet/Moon/Asteroid?
- Counting Craters
- Radioactivity
Overtime, some atoms spontaneously split (decay) into smaller atoms
This creates two new atoms and releases energy
What is a half life? How do we use us to measure ages?
It is the time it takes for about half of the sample to decay from the original into a new type of atom
Used to measure ages through radioactivity (explained in the question before)
Be able to describe in detail what a liquid dynamo is, and how it generates a magnetic field on earth.
Liquid dynamo is when the outer core is molten and liquid is able to flow
This helps to produce Earth’s magnetic field
A liquid outer core means that it also has convection currents within it
-These create loops
What are the three ways we study Earth’s interior?
- Studying how the magnetic field shift and changes over time
- Measuring Earth’s gravitational field
- Using Earthquakes
What are the differences between P and S waves?
-P waves are pressure or compression waves
- They Travel by compressing the material in front of them
- They are faster
S waves are shear waves
- They Travel more slowly
- Cause much harder shaking
How can we use the differences between a P and S wave to determine how far away an earthquake’s epicenter is?
P and S waves travel at different speeds, by measuring the arrival times, we can determine how far the earthquake’s epicenter is
What is the theory of plate tectonics?
This is behavior of the plates at the boundaries between two plates moving over time
Be able to describe the different types of boundaries found where plates meet.
Divergent Boundaries:
- Where two plates are separating causing the material to upwell from underlying mantle
- Sometimes called spreading centers
- Mostly found under oceans
Convergent Boundaries
-Where two plates are moving together and once plate slides under the other
-Transform Fault Boundaries
Plates may also be moving in opposite direction to each other
A link between spreading zones and help facilitate subduction of rocks
What is a mid ocean ridge? How are they formed? What kind of boundary is this?
It is an elevated land under the ocean (like a mountain) which high levels of volcanic activity
The are formed when a new rock forms and as it cools it moves away from the spreading zone and contracts to form a newer ridge
What are the differences between the three main types of volcanoes?
Strato
- Subduction of plates results in the melting of the mantle to produce magma
- Produces thicker magma so it flows short distances
Shield
- A hot spot develops under the crust and magma rises through the crust and erupts
- Magma is fluid and will flow larger distances
Cinder cone
- Short lived volcanoes (active for less than 1 year)
- Occur by themselves and build up from pyroclastic material which is ejected
What is a caldera?
At the peak of many volcanoes there are craters which are 1km in diameter)
Describe the process that created the Hawaiian islands chain.
Formed by a hot spot occurring in the middle of the pacific plate
Provide some examples of locations in the solar system with volcanic activity.
The moon: Appears to be the same type of structure that creates low lying mare
Triton (Neptune’s moon)
Enceladus (Saturn’s moon)
The Earth has stayed hot since it formed over 4.5 billion years ago. This is partially due to heat retention (it held onto its heat from formation), but also due to continued heating by what?
Radioactive decay of materials in the crust
The Earth’s surface is relatively young. How old is it? and what is causing it to be resurfaced?
Few hundred million years old
Plate tectonics constantly shifting cause resurfacing
Why did the Moon cool off more rapidly?
Because it is so small
What is the dominant process that ‘sculpts’ the Moon’s surface presently?
Eons of asteroids and comments slamming into the moon’s surface has sculpted its shape
How is the Moon’s regolith created?
Meteorite impacts
Provide a basic description of the tidal force
Tidal forces occur when there is a difference in gravity between two sides of a celestial body caused by the attraction of another body
How are the tides created on Earth?
The moons gravitational pull causes the water in earth’s ocean to rise
What three effects ‘complicate’ the ocean tides?
- The Earth’s rotation drags tidal bulges out of line
- Coastlines cause high tides to occur in a pattern
- The sun contributes to tidal forces too
What effect does the Sun have on the ocean tides?
The sun is massive but further away, however, its gravitation force is much stronger
But since the moon is closer it has a larger effect on tides
What does it mean when we say the Moon is in a synchronous rotation with the Earth?
It is tidally locked
Explain how the Moon is slowly moving away from us.
Due to tidal forces
The tides slow the earth’s spin which increases the moon’s spin causing it to slowly move further away
How do we know the Moon is moving away from us?
Astronauts placed laser reflectors on the moon to measure motions
Describe how seismic waves change when they move from one type of rock to another
They bend according to the rock they pass through
What type of evidence do we have to prove that the Earth has differentiated?
Seismic studies show both the Earth and Moon increase in density at their cores
We can map the transition from dense core to mantle to the least dense parts
Why is the mean density of the Moon much less than the Earth
The interior of the moon is similar to the material on Earth’s mantle, making it less dense
What are the three basic factors that shape terrestrial surfaces?
Impacts with asteroids and comets
Erosion from liquid water and wind
Geological processes
Expand on what ‘geologic processes’ are, give some examples.
It is any form of geological activity
E.g. mountain ranges, earthquakes, sinkholes, etc.
How long does it take for the mantle to complete one full convection cycle
200 million years
