How deep is the earth?
6,4000 km deep
What is drilling?
way for scientists to probe the Earth's sediments, crust, and upper mantle
Deepest drill hole– 12 km
Marianas trench max 11km- is what we know
We have to learn about the interior of the earth through other observation
What is the different criteria used to discuss earth’s internal layers?
Chemical composition
Mechanical behavior of materials
When a force is applied=how they respond
How many many layers is the earth composed of?
3
Outer: crust, Mantle, Innermost: Core (boiled egg)
How do we know the layers are there?
Measured through seismic waves which are measured at stations across the earth
the speed of these waves increases with density and as you go deeper into the earth the density of rocks increases due to presuure from overlying rocks
Major change in seismic wave velocities=the density is significantly changing–seismic discontinuity
These changes say there are different layers
What are the differnet kinds of earthquake waves?
P-wave (body wave), S-wave (surface/shear waves)
P-waves travel through compression and decompression
P-waves are faster
P-waves can travel through solids (rocks and minerals) and fluids (water and magma). S-waves can only travel through solids.
How are these waves read?
Seismic station is where a sensor is
P-wave arrives first and then the s- wave arrives later
Speed is determined on the function of the property of the rock
Less dense=slower dense=faster
Affects both waves
What is the crust?
thick outer shell of rock, referring to less than (<) 1% of the planets radius and volume
2 types: continental and oceanic
What is continental crust?
Thicker—Avg–25-30 km, but avg can vary (Himalayas-thick crust (80km))
30% of crust and high elevation
avg composed of granite (density 2.6-2.7g/cm relative to water)
Continents are formed at higher elevations because basalt/oceanic crust is floating on the earth's mantle, continental crust floats higher (forms ocean basisn)
What is oceanic crust?
Thinner—Avg 5-7km—Fairly uniform in thickness
70% of the crust and low elevation
made of basalt (density: 2.9-3g/cm relative to water)
What is a hypsometric curve?
shows the proportion of the earth's surface at a certain elevation
Distribution of land surface relative to sea level
Continental shelf: edge of a continent that lies under the ocean (submerged)
What is the mantle?
Largest and thickest layer
82% of Earth by volume
Generally solid rock despite magma, but can behave like a fluid sometimes (over long tome scales, the rock can move)
Seismic wave activity increases
Show a sharp increase in speed from the base of the crust to the top of the mantle
Divisible into
Upper mantle (base to 410 km depth)
Transitional mantle (mineralogical changes)
Lower mantle (660-2,900km)
What is the upper mantle composed of?
ultramafic rock peridotite
Peridotite–most common mantle rock
Basalt is volcanic, magma is formed in mantle, and as its moved up it carries fragments of the mantle (Xenolith)
Xeno=foreign Lith=Rock, foreign rock
Ultramafic–extremely rich in iron and magnesium (even more dense)
Why is the mantle similar to a pot of water heated from below?
Below certain depth, mantle convects
Convection currents occur due to density differences caused by variations in temperature and composition
As it heats up, the bottom gets hotter and moves up and cold comes down—Convection cell
Over long time scales, the mantle can slowly move/flow
Over short time scales it behaves as a solid
What is the core?
17% of Earth by volume
Base of mantle to center
composed of outer and inner core
Core has a composition similar to iron meteorite
Shooting stars that reach earth and they have a crust, mantle and core
What is the outer core?
Liquid iron and nickel
Know because of seismic waves
P-wave speed decreases, and s-waves don't travel through
What is the inner core?
Solid
Primarily composed of iron and nickel
How is earths magnetic field produced?
Outer core flows around the solid inner core generates earth's magnetic field (the motion creates the magnetic field)
What does the magnetic field do?
shields us from high energy radiation from the sun
Also use for navigation
Interacts with solar waves and protects us
Interaction between high energy particles and magnetic field creates aurora
What are compositional layers?
continental and oceanic crust, mantle and core
Behavior of the layers is different how they respond to force
What are the mechanical layers?
The lithosphere, the asthenosphere, the mesosphere, the outer core, and the inner core
How do the layers act?
The crust and a bit of the upper mantle behave in a rigid way (break rather than flow)
lithosphere doesn’t take part in convection
Asthenosphere–convects
Lower mantle is also rigid-pressure is too high–Mesosphere
Outer core convects, inner is solid rock so doesn't convect because of high pressures
What is the lithosphere?
the outermost physical layer of the earth (crust and upper part of mantle)
Diamonds form because its thick and there's high pressure
2 types: oceanic and continental
It is broken into segments called plates
What is the asthenosphere?
from the base of the lithosphere to the transitional mantle
moves and flows due to convection currents created by heat coming from the earth’s core
is relatively unbroken (determined this by analyzing seismic waves that pass through the layers)
What is the mesosphere?
the lower mantle, is more rigid due to high pressures and temperatures
Located at a depth of approximately 410 and 660 km below the earth’s surface
extreme conditions create a transition zone in the upper mesosphere where minerals continuously change