atmosphere and hydrosphere Flashcards
what percentage of earth is fresh water
3%
What was the main source of the Earth’s atmosphere?
volcanic eruptions
The four layers of the Earth’s atmosphere are
Troposphere, Stratosphere, Mesosphere, Thermosphere
What is evaporation
Water getting warm and changing from liquid water to water vapour
Snow and hail are examples of
precipitation
What term is the measure of dissolved salts in water?
salinity
what dominates the atmosphere on Earth?
carbon dioxide
Water is an excellent solvent for many substances. What is a solvent
The substance that does the dissolving in a solution
what is the substance dissolved in a solution is
solvent
The loss of water from plants in the form of water vapour is called _____________
transpiration
Describe the role of Cyanobacteria in the development of life on Earth?
Cyanobacteria are photosynthetic. They convert sunlight into energy and produce oxygen as a waste product. Back then, the Earth’s atmosphere didn’t have free oxygen in it as it does today. It was locked up in water molecules, or bonded to iron in minerals.
Describe the effects of oxygen on the oceans and on land.
When the oceans first formed, the waters must have dissolved enormous quantities of reducing iron ions, such as Fe2+.
These ferrous ions were the consequences of millions of years of rock weathering in an anaerobic (oxygen-free) environment.
The first oxygen produced in the oceans by the early prokaryotic cells would have quickly been taken up in oxidizing reactions with dissolved iron.
This oceanic oxidization reaction produces Ferric oxide Fe2O3that would have deposited in ocean floor sediments.
The earliest evidence of this process dates back to the Banded Iron Formations, which reach a peak occurrence in metamorphosed sedimentary rock at least 3.5 billion years old.
Most of the major economic deposits of iron ore are from Banded Iron formations.
These formations, were created as sediments in ancient oceans and are found in rocks in the range 2 - 3.5 billion years old.
Very few banded iron formations have been found with more recent dates, suggesting that the continued production of oxygen had finally exhausted the capability of the dissolved iron ions reservoir.
At this point another process started to take up the available oxygen.
Once the ocean reservoir had been exhausted, the newly created oxygen found another large reservoir - reduced minerals available on the barren land.
Oxidization of reduced minerals, such as pyrite FeS2, exposed on land would transfer oxidized substances to rivers and out to the oceans via river flow.
Deposits of Fe2O3that are found in alternating layers with other sediments of land origin are known as Red Beds, and are found to date from 2.0 billion years ago.
The earliest occurrence of red beds is roughly simultaneous with the disappearance of the banded iron formation, further evidence that the oceans were cleared of reduced metals before O2began to diffuse into the atmosphere.
Finally after another 1.5 billion years or so, the red bed reservoir became exhausted too (although it is continually being regenerated through weathering) and oxygen finally started to accumulate in the atmosphere itself.
This signal event initiated eukaryotic cell development, land colonization, and species diversification.
The oxygen built up to today’s value only after the colonization of land by green plants, leading to efficient and ubiquitous photosynthesis.
The current level of 21% seems stable.
Once oxygen had been produced, ultraviolet light split the molecules, producing theozone UV shieldas a by-product.
Only at this point did life move out of the oceans and respiration evolved
Describe how the ozone was formed.
Ozone is naturally produced in the stratosphere by a two- step reactive process. In the first step, solar ultraviolet radiation (sunlight) breaks apart an oxygen molecule to form two separate oxygen atoms. In the second step, each atom then undergoes a binding collision with another oxygen molecule to form an ozone molecule. In the over- all process, three oxygen molecules plus sunlight react to form two ozone molecules.
The ozone layer form by photolysis - the decomposition or separation of molecules by the action of light.
Outline the role of the ozone layer in the atmosphere.
the ozone layers is a protective layer of the stratosphere
In what layer in the atmosphere is the ozone layer located?
stratosphere
