Earth and other planets

Question 1

Formation of elements timeline

Answer 1

1. Big bang: Protons and neutrons form followed by H, He and Be
2. Star formation: Gases come together under gravity, heat/pressure rise and fuse H into He, nuclear fusion produces heavier elements up to Fe
3. Death of stars: Large stars explode in a supernova, producing last of the heavy elements.

Question 2

Planet formation, Accretion

Answer 2

1. Rock formation from compression of dust

2. Rocks begin colliding, because of runaway gravity, and combining

Question 3

Planet formation, Differentiation

Answer 3

1. Heat melts the planet
2. Heavy elements like Fe and Ni sink to the centre of the molten planet.
3. Lighter elements rise to the crust
4. Eventually, the crust cools

Question 4

During differentiation of a planet, how do the gain enough heat?

Answer 4

Formation of the planet itself, asteroid impacts and radioactive elements

Question 5

Structure of the earth (outside to inside), plus key property of each layer

Answer 5

Hydrosphere and atmosphere - Oceans and air
Crust - Solid rock
Mantle - Mostly solid rock, made of silicate minerals
Outer core - Liquid Fe and Ni
Inner core - Solid single crystal of Fe and Ni

Question 6

4 types of seismic waves

Answer 6

Primary, secondary, love and rayleigh

Question 7

P-waves

Answer 7

Faster than s-waves
Travel through solid AND liquid
Particles move in direction of travel
Refract when moving into liquids

Question 8

What is the name of waves where particles move in the direction of travel?

Answer 8

Compressionable waves

Question 9

S-waves

Answer 9

Slower than p-waves
Can’t travel through liquids
Particles move perpendicular to direction of travel

Question 10

S-waves and imaging the earth’s core

Answer 10

1. S-waves don’t travel through liquid

2. There is an s-wave shadow zone below epicentre suggesting liquid outer core

Question 11

P-waves and imaging the earth’s core

Answer 11

1. P-waves travel through liquids but refract as they enter them
2. Another refraction of the waves as they travel through the earth shown by gaps in P-wave shadow zones.
3. This suggests solid and liquid layers to the core
4. Because s-waves cannot travel through liquid, and has a larger shadow zone, outer layer must be liquid and the inner solid

Question 12

Moho discontinuity

Answer 12

Boundary between crust and mantle

Question 13

Lithosphere

Answer 13

Consists of crust and rigid mantle

Question 14

Asthenosphere

Answer 14

Consists of soft part of upper mantle, below lithosphere

Question 15

Transition zone

Answer 15

Boundary between upper and lower mantle

Question 16

Formation of atmosphere

Answer 16

1. Volcanic degassing
2. Comets and asteroids carrying materials onto earth
3. Presence of life, i.e. respiration/photosynthesis

Question 17

Definition of a rock

Answer 17

Naturally occurring solid composed of at least one mineral

Question 18

Definition of a mineral

Answer 18

Solid, ordered crystal structure, naturally occurring, inorganic, characteristic chemical composition

Question 19

Igneous rock

Answer 19

Formed from freezing magma

Question 20

Sedimentary rock

Answer 20

Forms when rocks are broken down, transported and redeposited

Question 21

Metamorphic rock

Answer 21

formed by adding heat and pressure to igneous and sedimentary rock

Question 22

Ages of rock, relative ages: Law of superposition

Answer 22

In undeformed stratigraphic sequences the oldest rock is at the bottom

Question 23

Ages of rock, relative ages: Cross cutting

Answer 23

If a rock unit crosses across other rocks, that rock must be younger

Question 24

Ages of rock, absolute ages: Radiometric dating

Answer 24

Radioactive isotopes half lives can be used to calculate when a rock was formed by observing the ratio of parent to daughter elements

Question 25

Climate definition

Answer 25

The weather conditions prevailing in an area, in general, over a long period of time

Question 26

Weather definition

Answer 26

State of the atmosphere at a particular place and time