Earth's Internal Heat Flashcards
layers of the earth
crust, mantle, outer core, inner core
Solid, rigid, outermost layer; broken into many pieces called plates.
* Transformed by exogenic due to the interaction of subsystems and endogenic processes caused by the earth’s internal heat
crust
what elements are abundant on the rocks of the crust
silicates and aluminum (SiAl layer)
oceanic crust
6-12 km, denser, basaltic
continental crust
25-70 km thick, less dense, granitic
temperature of crust
200°-400° C near the Moho
Rocks are semi-solid; partly molten, and can flow
processes: Convection current - the circular motion of semi-solid materials due to the heat from the core
- upper and lower
- thickest layer
mantle
what elements are abundant on the rocks of the mantle
silicates and magnesium (SiMa)
how hot is the mantle
1000-3000 C
how thick is the mantle, and what percent of the earth’s volume is it
2900 km; 83%
zone of Earth’s mantle lying beneath the lithosphere and is believed to be much hotter and more fluid than the lithosphere.
- where magma is found
asthenosphere
Liquid layer; rich in iron and nickel
(NiFe layer)
* The convection flow of materials
generates the _____________________
outer core; earth’s magnetic field
how thick is the outer core
2,200 km
how hot is the outer core
4,500-5,500 C
Extreme pressure from overlying
squeezed the metals together
making this layer solid (Pressure
freezing)
* This layer’s gravitational force pulls all other layers towards itself
inner core
how thick is the inner core, and what elements are abundant in it
1250 km radius; NiFe
how hot is the inner core
5430-6000 C (hotter than the surface of the sun, hottest layer)
the solid, outer part of Earth. includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth’s structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below
lithosphere
beneath the asthenosphere. It encompasses the upper mantle and lower mantle (where material still flows but at a much slower rate than the asthenosphere.)
mesosphere
Earth’s most internal layer beneath the lithosphere. It is the innermost layer of the Earth and includes both the inner core and outer core and is composed of nickel and iron.
barysphere
The transition zone between upper and lower Crust.
Conrad Discontinuity
The transition zone between the Crust and Mantle
Mohorovicic Discontinuity
The transition zone between Outer mantle and Inner mantle.
Repetti Discontinuity:
The transition zone between Mantle and Core.
Gutenberg Discontinuity
The transition zone between Outer core and Inner core.
Lehmann/Bullen Discontinuity
The faster of the two types of body waves; they travel through solids and liquids but travel more slowly through liquids than solids
-can pass through both mantle and core, but are slowed and refracted at the mantle / core boundary at a depth of 2900 kms
- evidence for the solid inner core
P-waves
The slower of the two types of body wave; not transmitted by liquids (or other fluids)
- this passing from the mantle to the core is absorbed because it cannot be transmitted through liquids. This is evidence that the outer core does not behave like a solid substance
- This produces a ‘shadow zone’ on certain parts of the Earth’s surface where S-waves are not recorded, and this is used as the main piece of evidence to deduce the size of the core. The core has a radius of 3470 km.
s-waves
how are the properties of the earth’s layers discovered
through seismic waves
how is the temperature of the core assumed
since the core generates the earth’s magnetic field that is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in the Earth’s outer core, it was assumed that the core is made up of iron and nickel. these compositions’ melting point is the core’s assumed temperature
the transfer of kinetic energy from one medium or object to another, or from an energy source to a medium or object.
heat
why is the earth’s interior hot?
due to the primordial heat and radioactive heat
the internal heat energy accumulated by dissipation in a planet during its first few million years of evolution. The main contributions to the primordial heat are accretional energy – the energy deposited by infalling planetesimals – and differentiation energy.
- ancient heatLeftover heat from Earth’s
Formation (Planetary
Accretion) - Friction due to the movement of
heavy metals
early - rocks - inelastic collision - kinetic energy - heat - giant ball of lava/magma - cool down - stabilize - forming layers (bc of density) - movement - friction of metals - heat
primordial heat
Any of innumerable small bodies of accreted gas and dust thought to have orbited the Sun during the formation of the planets
planetesimals
meteoroid vs. meteor vs. meteorite
When meteoroids enter Earth’s atmosphere (or that of another planet, like Mars) at high speed and burn up, the fireballs or “shooting stars” are called meteors. When a meteoroid survives a trip through the atmosphere and hits the ground, it’s called a meteorite.
Radioactive isotopes such as U-238, Th-232, K-40 in the core of the earth undergo spontaneous fission to produce more stable isotopes/elements. (radiation but very short, probably in mantle or crust)
radiogenic heat
How does Heat travel
in the layers?
through
- conduction (from the inner core to the outer core)
- convection (outer core and mantle)
- radiation (radioactive isotopes)
Transfer of heat in solid through direct contact
conduction
Transfer of heat in fluids
(liquid and gas) through the circulation of matter
convection
Transfer of heat through space by
waves
radiation
The extreme temperature of the inner core could have molten the iron and nickel but it is believed to have solidified as a result of
pressure freezing
The temperature of the inner core is far above the melting point of iron. However, the inner core’s intense pressure—the entire rest of the planet and its atmosphere—prevents the iron from melting.
