Planet Earth As A System

Question 1

Features of the atmosphere

Answer 1

Gaseous envelope
90% of mass in lower 11km
Conventionally, upper limit set at 100km
Mostly nitrogen>oxygen>argon>CO2 with other minor gasses
Also variable amounts of water vapour
Originates from geosphere through volcanoes
Very thin

Question 2

Features of hydrosphere

Answer 2

Liquid water covers ~70% of earths surface as oceans
Oceans make up 97.5% of all surface water
Water also lies on land surface as rivers,makes and ice making up 2.5% of which only 0.01% is liquid
Originates from earths interior through volcanoes

Question 3

What are the layers of the geosphere?

Answer 3

Core - metallic iron, molten outer core flow - cause of magnetic field
Mantle - solid, rocky layer, hot and ductile. Locally melts to generate “magma”, hot and dense
Crust - outermost rocky layer, rocks have lower density and are colder than underlying mantle
Lithosphere - stiff utter rocky shell, consists of two parts the crust and the uppermost mantle

Question 4

What are the three plate boundary types?

Answer 4

Divergent (constructive) - ocean floor spreading, magma generated and new oceanic crust is created
Convergent (destructive) - subduction of ocean lithosphere, magma generated and new continental crust generated
Transform (conservative)

Question 5

What are deep ocean hydrothermal vents?

Answer 5

Black smokers
Driven by magmatic heating at mid oceanic ridges
Ecosystems not dependant on solar energy
Origin of life may have began here

Question 6

What happens at subduction zones?

Answer 6

Oceanic lithosphere sinks (subducts) when >180 million years old
Pulls continents together and closes ocean basin
Continents too light to subduct so they collide and plate subduction ceases
This is how mountains and volcanoes are formed

Question 7

What drives plate tectonics?

Answer 7

Solid mantle rock circulates in large convection cells
Carrying slabs of rigid plates along the surface
And dragging them back into the interior
Solid material can flow because hot metal is ductile

Question 8

What role does heat driven convection play in the earth system?

Answer 8

Material and energy are transferred between the spheres
Heat sources are -radioactivity
- energy left over from earths formation
- solar irradiation
Heating causes material to become less dense and it rises
Heat is lost to space and materials become less dense and sink

Question 9

What is the biosphere?

Answer 9

The realm of living organisms
Lower atmosphere to uppermost lithosphere, including all levels of the oceans
Existed on earth for at least 3.8 billion years and major factor in planetary development

Question 10

How does the biosphere influence earth?

Answer 10

Moderates greenhouse effect by converting CO2 into organic matter, hence influences climate
Emits gaseous oxygen to atmosphere and oceans
- highly reactive
- unusual in planetary atmospheres
- Toxic to many primitive micro-organisms
- essential for animal respiration
Removes and redistributes chemical constituents of rocks (nutrients) hence alters rocks aiding soil formation

Question 11

What is biogeochemical cycling and name 2 examples

Answer 11

A pathway through which a chemical element or molecule moves between biological and environmental components of an ecosystem
Eg - greenhouse gasses, phosphorus and sulphur cycles

Question 12

Describe the global phosphorus cycle

Answer 12

Tectonic processes uplift rock to the surface
Wind and rain erode phosphorus rich rock
Run off carries sediment to rivers, lakes and oceans
Plants use phosphorus from soil
Animals eat plants
Decomposers return phosphorus to the soil
Run off of phosphate bearing compounds in fertilisers
Phosphorus leaches from the soil into the water
Sediment accumulates to form phosphate-rich sedimentary rocks

Question 13

Describe the global sulfur cycle

Answer 13

Tectonic processes uplift rocks and weathering breaks down sulfur bearing minerals
Humans burn fossil fuels giving off sulfur compounds
Volcanoes release hydrogen sulfide gas
Rain combines with hydrogen sulfide to make sulphuric acid
Acid rain increases weathering of rocks
Rivers transport dissolved sulphur to water bodies
Plants use sulphur bearing compounds in soil
Animals eat plants
Decomposers produce hydrogen sulfide which reacts with iron to produce pyrite
Sulfur is leached from soil and is transported to water
Sulfur precipitates as sulfate and sulfide minerals

Question 14

What layers can the Earth be divided into?

Answer 14

Geosphere
Hydrosphere
Biosphere
Atmosphere