c9 Flashcards
(40 cards)
what is the earths atmosphere like today
-78% nitrogen
-21% oxygen
-small % of other gases (water vapour,carbon dioxide,noble gases)
what was the earth like in the first billion years
-scientists believe there was large amounts of volcanic activity
-these volcanoes formed the early atmosphere
how were the oceans formed
-as the oceans cooled the water vapour condensed to form the ocean
what was the earths early atmosphere like
-consisted of mainly carbon dioxide with little or no oxygen due to volcanic activity
-volcanoes also released nitrogen and small amounts of methane and ammonia
how did carbon dioxide levels decrease in our atmosphere
-dissolving in oceans
-photosynthesis
-carbon being trapped in fossil fuels
how did carbon dioxide dissolve in the oceans
-some of the carbon dioxide dissolved in oceans to form a weak acid
-this reacted with minerals in the sea to form precipitates
-and over time this formed sediments of carbonate rock on the sea bed
what was the carbon dioxide in the sea used for
-carbonate rock
-some formed corals and shells of organisms
-when these animals died they formed limestone and released carbon dioxide
where did the oxygen in the atmosphere come from
-2.7 billion years ago photosynthetic algae first evolved in the oceans
-photosynthesis produced oxygen
-over the following billion years,plants evolved increasing the amount of oxygen in the atmosphere
what are fossil fuels
-formed over millions of years
-non renewable
how is coal formed
-formed from the remains of ferns and trees
-if they die in marshy wetland then they do not decompose due to a lack of oxygen or acidic conditions
-over time these plant remains are covered with sediment and compressed
-high temperature and pressure creates coal
how is oil formed
-when plankton die they settle in mud on the sea bed
-if oxygen is not present they will not decompose
-over time they are compressed by sediment
-heat and pressure convert them into crude oil
how is natural gas formed
-natural gas is mostly methane
-find natural gas near deposits of oil
-formed from plankton in a similar way to oil
what do all fossil fuels contain
-trapped carbon
-that carbon was part of the carbon dioxide taken in by photosynthesis
what are examples of green house gases
water vapour,carbon dioxide and methane
what is the natural greenhouse effect
-energy from the sun travels to the earth as short wavelength radiation
-some short wave radiation reflects back into space but most of it easily passes through the atmosphere
-energy of radiation is absorbed by the earths surface
-surface of the earth radiates the energy back as longwave radiation which can react with the greenhouse gas (absorb)
-due to energy being trapped in the atmosphere the temperature increases
why can short wavelength easily pass through the environment
-does not interact strongly with gas molecules in the atmosphere
what does the natural greenhouse effect do
keeps temperature warm enough to support life
what is the effect of the increase of human activity in the atmosphere
-levels of carbon dioxide and methane are rising
why are the levels of carbon dioxide increasing in the atmosphere
-burning of fossil fuels
-eg coal for electricity
-deforestation
-burning forests releases large amounts of carbon dioxide
why are levels of methane increasing in the atmosphere
-methane is released in agriculture for example growing rice in flooded paddy fields
-released when cattle pass wind
what does the rising levels of methane and carbon dioxide mean for the environment
-temperatures of the atmosphere is rising
as more energy from the sun is trapped
what do the rising temperatures mean for the environment
-increase melting of polar ice sheets and glaciers which leads to increased sea levels
-increased sea levels could lead to flooding of low lying areas
-could lead to more severe weather in the uk
what does rising temperatures mean for animals
-could change the distribution
-could change distribution of insect born diseases
what do scientists believe climate change is caused by
-human activity causing release of greenhouse gases
