Earth Systems

Newton’s Law of Universal Gravitation

f= force

G= gravitational constant (6.6743×10⁻¹¹ m³ kg⁻¹ s⁻²‍)

m1= mass of object 1

m2= mass of object 2

r= distance between centres of the masses

Hydrostatic Equation

P= pressure at bottom of water column

Pw= density of seawater (assuming uniform; 1028kg m^-3

gh= height of water column (m)

What are meteorites?

Natural objects originating in outer space that survive an impact with the Earth’s surface.

What are xenolith?

Rock fragments that are transported by a magma and subsequently found within it.

They provide important information about the otherwise inaccessible mantle.

Moment of Inertia of Earth

How difficult it is to spin.

Preliminary Reference Earth Model (PREM)

Crust to Core:

 

1)        The Moho: crust-mantle boundary- a sharp discontinuity in seismic velocity where igneous and metamorphic crustal rocks are underlain by mantle peridotite. 7-11/12 km

2)        The Low-Velocity Zone: ~100km depth with evidence that part of the upper mantle is less rigid and may be partly molten. This is the top of the asthenosphere, below the rigid lithosphere (crust and upper mantle)

3)        Mantle transition zone: a change from mainly peridotite above to rock with higher density minerals below.

4)        Lower mantle: gradual increase in v_p and v_s- increasing rigidity of minerals with increasing pressure.

5)        The Core: probably dominated by iron or nickel-iron. The outer core is molten and the inner core is solid. The outer core must have ~10% lighter elements (O, S, Si, K, H) to match the calculated seismic velocities.

What does the magnetic field do?

Deflects charged particles of the solar wind that would otherwise strike Earth and destroy the atmosphere.

Key changes through geological time

1) Amount and distribution of solar radiation received by Earth’s surface

2) Surface character of the Earth and distribution of continental plates

3) Composition of the atmosphere

4) Living things on Earth

5) Magnetic field

What are cyanobacteria?

Photosynthetic bacteria that appeared on Earth about 2.5 billion years ago

What was the Great Oxidation Event?

When oxygen levels in the atmosphere increased to appreciable levels.

Characteristics of Hardness

Resistant to scratching and indentation- measured on Mohs Relative Hardness Scale

Ionic bonds

Moderate strength- ± poles stick togetheroC

Covalent bonds

Atoms share electrons in the outermost shell, strong

Metallic bonds

Electrons are ‘free’ / delocalised making them electrically conductive

What bonds do calcite have?

Covalent and ionic

Mineral Group 1

Silicates- contain SiO4

Feldspars are the most common crustal mineral

Mineral group 2

Silicates containing Fe and Mg- Olivine, Amphibole and Pyroxene

What does viscosity affect?

Gas escape

Lava flow velocity

Eruptive style

Crystal growth

Bubble rise/crystal settling

Magma ascent rate through crustS

Strombolian eruptions

Short-lived

Explosive

Can form scoria coneB

Vulcanian eruptions

Canon-like explosions

Short-lived

High velocity

Compressive stress

Stefan Boltzmann Equation

E = σ T4
σ is the Stefan-Boltzmann constant
(5.673 x 10-8 J m-2 s-1 K-4 )

What does the Stefan Boltzmann Equation calculate?

The total energy radiated per unit area per unit time (or power) by a black body at a given temperature.

What is temperature in K?

Temp in C + 273K

Sun’s surface temperature in K

6000K

Lapse rate

The rate of change in atmospheric temperature as it decreases with height.

Lapse rate of dry air (DALR)

9.8^oC/km

Stratosphere

10km-50km above Earth

Temperature increases through this layer due to ozone.

Mesosphere

50km-100km above Earth

Strong atmospheric tides

Little moisture

Coldest place in Earth’s atmosphere (low as -140^o)

Thermosphere

100km-500km

Temperature increases with height due to absorption of solar radiation by atmospheric molecules

Exosphere

Gas molecules are not gravitationally bound to Earth near the bottom of the exosphere

Thin envelope of lightest gases (hydrogen/helium)

Ocean surface temperature is increased by…

Short-wave solar radiation absorbed by the surface ocean

Conduction between a warm atmosphere and a cold ocean

Ocean surface is decreased by…

Long-wave back radiation emitted by the ocean surface

Conduction between warm ocean and cold atmosphere

Evaporation

Salinity of surface ocean is increased by…

Evaporation

Sea ice formation

Salinity of surface ocean is decreased by…

Precipitation

Sea ice melting

Input of freshwater by rivers

Ideal Gas Equation

P= pRT

Pressure- gradient force

This causes air to move from regions of high pressure to regions of low pressure

Isobaric surfaces

Surfaces of constant pressure

Why doesn’t Earth have a single cell convection?

Earth rotates and Coriolis force causes moving air and water to turn

Coriolis parameter

This describes the magnitude of the effect of Coriolis force at a specific location

• f = 2 * Ω * sin(φ), where Ω is the Earth's angular velocity and φ is the latitude. 

• In the N hemisphere, f is positive because latitude is positive

• At the equator f is zero

• In the S hemisphere, f is negative because latitude is negative

Coriolis force

CF= 2Ω sin θ v

To understand how the movement of Earth effects moving objects in the atmosphere and oceans.

Processes of poleward heat transport in the atmosphere

1) Latent heat

2) Hurricanes

3) Baroclinic waves

Ekman spiral- consequence of Coriolis effect

Where winds exert a frictional force (wind stress) on the surface layer of the ocean.

Initially the surface layer is pushed in the same direction of the wind.

As soon as water starts to move, Coriolis force acts upon it and the curren turns to the right (in NH)

Surface layer exerts a frictional force on layer beneath, causing this to also turn right and so on…

Ekman transport

Net transport in the Ekman layer is perpendicular to the wind (right in NH and left in SH)

Causes either upwelling or downwelling dependent on wind direction in relation to coastline and which hemisphere you are in

Importance of Upwelling

Brings nutrient rich water from deep layer to the surface in the photic zone.

These can be utilised by phytoplankton, increasing primary productivity and biomass up the food chain.

These regions are commercially important for fisheries (especially sardines and anchovies.

Anti-cyclone (high pressure)

Atmospheric pressure distribution in which there is a high central pressure relative to the surroundings.

Characterised by large areas of stagnant weather conditions which are often dry and settled.

Closed isobars on a synoptic weather chart

Mid-latitude cyclones (low pressure)

Air is generally rising vertically through the atmosphere- as it rises and cools water vapour condenses to form clouds and can often lead to precipiation

Weather is often cloudy, wet and windy

Cold front typical weather conditions

Sharp wind veer

Band of rain ahead and along

Cold and dry conditions follow as front passes

Warm front typical weather conditions

Cool with increasing cloud

Winds often ‘back’ from an easterly to southerly direction

Warmer, more humid air after it passes

What are Eddies?

The oceans’ weather- longer lasting than atmospheric systems, for months to years.

Sometimes referred to as rings

Why are Eddies important?

Contain a different water mass (temp and salinity) to surrounding water

This means that they are a form of transport of heat and salt between water masses (aka. Eddie mixing)

May also contain different nutrients and plankton species to surrounding water leading to plankton blooms

High cloud examples

Cirrus

Cirrostratus

Cirrocumulus

Medium cloud examples

Altostratus

Nimbostratus

Altocumulus

Low cloud examples

Stratus

Cumulus

Cumulonimbus

Tritiu, (³H)

Radioactive isotope of hydrogen with two neutrons and one proton

Half-life of ~12 years

What generates tsunamis?

Undersea earthquakes or landslides

Vertical movement of the seabed causes a displacement of the sea surface that ravels away as a surface gravity wave

Examples of tsunami warning systems

Seismometers to detect

Model simulators help predict their path and size

Sirens and public alarms for evacuation

Land-based temperature observations

Stevenson screen (1.25m above ground level, wet and dry bulbs)

Land-based rainfall observations

Tipping bucket rain gauge (copper gauge about 450mm above ground level)

Sunshine/solar radiation observations

Campbell-stokes sunshine recorder and pyranometers

Wave properties

Height

Amplitude

Wavelength

Phase speed