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