Chapter 9 Flashcards
what does the atmosphere consist of today?
21 oxygen
78 nitrogen
small proportions of other gases eg water vapour co2
= stayed constant for 200 million years
why can’t scientists be sure of earth early atmosphere?
what do they think happened during first billion years?
can’t be sure as earth is 4600 million years old
They think during first billion years = intense volcanic activity
explain what scientists though intense volcanic activity did…
released gases that formed the atmosphere
one - water vapour
earth cooled water vapour condensed to form Oceans
two- carbon dioxide
early atmosphere mainly carbon and little or no oxygen
like MARS AND VENUS TODAY
Three- other gases included nitrogen
= built up the atmosphere
and small amounts of ammonia and methane
MAINLY CO2 BUT INCREASING AMOUNTS OF NITROGEN
state differences between atmosphere then and now?
early atmosphere- large amounts of co2 BUT NOW
only small amount
Also then little or no oxygen now 21%
Why carbon start dropping?
Water vapour condensed = formed oceans
Some carbon dioxide dissolved in the ocean to form weak acid
This reacted with minerals in the sea to form PRECIPITATES
over time formed sediments if carbonate rock on the sea bed
Some of the carbon In the sea was used to make corals and Shells of organisms such as mussels
When they died formed sedimentary rock limestone
CO2 began to drop
Where did oxygen come from
2.7 billion years ago photosynthetic algae first evolved in the oceans
Photosynthesis produced oxygen which entered the atmosphere
Over the following billion years plants evolved and increased the amount of oxygen in the atmosphere
At some point level of CO2 reaches the point where animals could evolve
what is the greenhouse effect? 7 steps
1 energy from the sun travels to the earth as short wave radiation
2 some short wavelength radiation is reflected back into space but most of it passes through easily
3 energy of radiation is absorbed when reaches earth surface
4 surface of earth now radiates long wave length radiation from earth surface
5 some long wave rad interacts with the greenhouse gases in the atmosphere
6 energy is absorbed
7 temp of atmosphere increases and is trapped
what does greenhouse effect do for humans?
Keeps temp on earth warm enough to support life without it would be too cold for most living organism
why has carbon dioxide increased today?
we burn fossil fuels
we burn for electricity petrol diesel
DEFORESTATION - no trees to absorb and large amounts released
why has methane increased today?
released in agriculture - growing rice in paddy fields
when cows pass wind
what effect does increasing carbon Dioxide and methane have of earth?
Temp of atmosphere is rising as more energy from sun is trapped
Increase melting of ice caps = increased sea levels = more flooding of low lying areas
Climate change- lead to more severe weather
Increasing temp- change distribution of animals such as insects
what do scientists believe climate change is caused by?
human activity causing release of greenhouse gases
BECAUSE
evidence shared between many different scientists
= they critic evidence and decide whether valid = peer review
Allows scientists to detect false claims
What is the carbon footprint?
Gives us an idea of how much something contributes to climate change
= total amount of carbon dioxide and other greenhouse gases emmited over the full cycle of a product service or event
how can reduce carbon dioxide emissions?
use insulation in homes and put heat down can reduce co2 emmisions and fossil fuel burning
Use public transport such as trains and buses - cars emit loads of co2
Switch to renewable resources of electric such as wind power
At home energy saving light bulbs or turn appliances off by plug
How can reduce methane emissions?
People eat less beef and less dairy products as methane come from agriculture BUT
people enjoy eating these and are unlikely to change diets
Methane- in landfills - reduce this by trapping methane and burning to produce electricity
AS methane is such a more powerful greenhouse gas than co2 = good Idea BUT
COSTS MONEY
