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1

The earth system

A system is any assemblage or combination of interacting components (for example the human body)

The earth system has four major interacting parts, with flows of matter and energy between them.

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What are the four major earth systems?

Biosphere
Atmosphere
Hydrosphere
Geosphere/lithosphere

3

What is anthroposphere ?

Human impacts and the built environment

4

Geosphere/lithosphere

Rocks and sendimemts.

The solid earth. The upper part of the solid earth, which interacts with the other components of the Earth System, is called lithosphere.

5

Atmosphere (a mixture of gases)

The air
Mainly nitrogen (N2) and oxygen (O2)
Carbon dioxide (CO2) essential for life.
Transfer of heat and light

6

Hydrosphere (totality of Earth's water)

Salt or fresh, liquid, or vapor
Surface waters, glaciers, and ground water
Cryosphere is the perennial frozen parts

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Biosphere

All the planet's living organisms
As well as recently decreased and decaying organic matter

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** Ecosphere

The term ecosphere includes the biosphere plus its interactions with the physical systems.

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Anthroposphere (human realm)

Anthroposphere =technosphere
- encompassed parts modified by humans
- interaction of the anthroposphere with other subsystems of earth = environmental science.

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Earth system science

In earth system science, the findings of physical and biological sciences are integrated into a global view of our planet.

This approach considers the complex interconnecting web of physical, chemical and biological processes, and the modifications of these processes and of the earth system's components through time.

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There are two sources of energy to fuel the earth system:
External energy and internal energy

External energy comes from solar radiation, which drives the hydrologic cycle and the circulation of atmosphere and oceans; these, in turn, cause erosion of the land surface.

Internal energy which drives volcanism and lithospheric deformation (plate tectonics) -- from radioactive decay in the earth's interior.

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Global change

The modification of the earth system's components and of the interactions between these components, both natural and human-induced, are referred to as global change.

** change is not a recent phenomenon, it is a characteristic aspect of the earth system.

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Types of global change

Gradual-- takes place over long periods of geologic time (millions to billions of years)
Catastrophic - takes place rapidly in geologic time (from seconds to centuries)
Unidirectional-- evolution o solid earth, evolution of atmosphere, evolution of life .
Cyclic-- supercontinent cycle, sea-level cycle, glacial-interglacial cycle

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Graphs of environmental systems in space and time

Graph shows characteristic spatial scale and time scale

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Example of natural change -- great oxidation event (GOE)

Caused by photosynthetic events inside the oceans. (Know more details)
GOE occurred around 2.4 billions years ago.
Evidences like red stone (the Fe2+ inside the rock are oxidized --rusty- red)

16

Human induced change? --weakening of the stratospheric polar vortex by arctic sea-ice loss

A recent study predicts that as the world gets warmer, parts of North America, Europe and Asia paradoxically could be hit by such cold snaps more often due to blasts of arctic air.

Shrinking sea ice could allow more energy to be transferred from the warmer ocean waters beneath it into the atmosphere.

That energy weakens and distend the polar vortex, which actually is a huge cyclone of swirling high-speed winds that keep cold air trapped in the arctic.
When the vortex weakens, it allows the cold air to slip southward.

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Population growth has driven our environmental impacts

Why so many humans?
-old Stone Age
-agriculture revolution
-industrial revolution
-medical-technological revolution

Human needs energy and resources!!

18

Human population bombed after industrial revolution-two reasons

The production of fertilizer from ammonia (but the cost of massive energy)
The improvement of health care

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Humans require energy

The results of this are:
Deforestation
Desertification
Enhanced greenhouse effect (climate change)
Loss of habitats and biodiversity
Air and water pollution
Soil degradation and erosion
Ozone hole
Ocean acidification
Acid rain

20

Our universe (introduction)

- the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them.
- created from a very small, dense conglomeration of matter and energy (called a singularity) that then exploded - the BIG BANG!

21

Aftermath of the Big Bang

-hot cloud containing only H (98%) and He (2%)
-gases clump into separate clouds (nebulae)
- collapse of nebulae leads to formation of protostars
- the high pressures and temperatures reached within protostars lead to nuclear fusion processes (fusion of hydrogen atoms to create helium atoms)

22

Stars: '' element factories''

1. Fusion reactions: fusion of H to produce He until H is used up, then fusion of He to form heavier atoms until He is consumed, and so on up to the formation of Fe in large stars (10-30 times the mass of the sun)

2. When a very massive star runs out of fuel, a very energetic explosion occurs, so that elements heavier than Fe are formed (supernova)
- Star death seeds the universe with heavier elements that mix with residual gas from the Big Bang.
- a subsequent generation of stars containing a larger proportion of heavier elements forms out of the more compositionally diverse nebulae.
- today 99% of the mass of the universe consists of H and He; only 1% is heavier elemental matter.

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Formation of our solar system

1. The Sun is a third - or fourth- generation star developed 5 b.y ago from a nebula that contained all 92 elements (99% H and He, the rest 1%)

2. Planets developed from the residual ring of dust and gas surrounding the newly formed Sun.

24

Formation of planets

1. The gas and dust from the protoplanetary nebula condensed into planetesimals that then clumped together to form protoplanets, and eventually true planets.
2. Inner, rocky planets made up of heavier elements: iron, magnesium, silicon and oxygen.
3. Outer, gaseous and icy planets made up of frozen gases and lighter elements: hydrogen (H), helium (He), methane (CH4) and ammonium (NH3)

25

Geologic time scale

** you need to know Eons:
Phanerozoic, Precambrian (it includes Hadean, Archean, Proterozoic)

** also know 3 recent Eras during Phanerozoic, they are Paleozoic, Mesozoic and Cenozoic.

** know the time boundaries between Eons and Eras: Precambrian is like 4 billion years ago, and Phanerozoic is 600 million years ago.
Paleozoic is like 542 million years ago, Mesozoic is like 252 million years ago, Cenozoic is like 66 million years ago.

** in addition, you also need to know what happens at those boundaries, more in lectures, or maybe tb..

** many division of the geologic time scale mark major environmental changes and biological changes (appearance or extinction of species)

26

The hadean eon: ''Hell on earth''
4.6 to 3.8 billion years before present
-- what happens internally

1. - Not much material from the early history of the planet survived.
- The oldest mineral grains come from sandstone in Western Australia and yield ages of 4.2 Ga (billion years)

Internal differentiation
- the energy from the accretion of the pro- Earth from planetesimals, early impacts, and radioactive decay was substantial and caused melting of the early earth.
- the molten state of the early earth led to internal differentiation (heavier elements such as iron and nickel settled towards the planet's center), which resulted in the formation of an iron alloy core and a rocky mantle.
''Very young, homogenous earth --> core is forming, mantle remains''

27

The Hadean eon: hell on earth

-- > conditions at surface

An initial magma ocean existed at surface
As the planet cooled, a thin igneous crust formed
Degassing of the mantle through volcanic activate contributed to the formation of an atmosphere of N2, NH3, CH4, H2O, SO2, HCl, CO2.
** no oxygen!
As the earth surface cooled, the water vapor in the atm condensed and rained onto the planet
Toward the end of hadean eon a global ocean existed
The primordial igneous crust was chemically weathered by rainwater and gases dissolved in it. The solid alteration products of these weathering processed became the first sediments of the earth.
'Prebiotic soup' -- ocean filled with organic molecules from abiotic reactions (made on earth and from meteorites --> all the ingredients for life

28

Archean Eon (3.8 -2.5 Ga)

--> atm changes and beginning of life

1. At the beginning of Archean the sun's luminosity was smaller by ~25 % than today, however, freezing conditions were not reached at surface because of an intense greenhouse effect
-- this is caused by greater amounts of greenhouse gases in the atm. E.g 100 times more CO2 than today that countered the effect of the faint young sun.

2. Others
Very different atm and ocean
Long term cycling of carbon was established
The establishment of this cycle and the position of the earth in the solar system were key factors in determining earth's surface temperature; the conditions on earth are not too hot and not too cold -just right to permit the earth to become a habitable planet (the Goldilocks effect)

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Archean Eon (3.8 -2.5 Ga)

--> atm changes and beginning of life (more)

The first possible evidence of life occur in 3.8 billion year old (Ga) rocks from Greenland
Fossilized filamentous cells in 3.5 Ga sedimentary rocks from Australia resemble modern-day photosynthetic Cyanobacteria (blue-green algae)
Archean stromatolites -evidence of widespread photosynthetic Cyanobacteria 3.4-3.5 Ga ago.
At some time prior to 2.5 Ga, photosynthetic organisms evolved that released oxygen into the environment.
Oxygen build up in our atm and oceans changed the surface conditions of our planet forever.
Sulfur isotopic signature revealed that before GOE, there is no ozone layer (anoxic atm), and after GOE, oxic atm (there is ozone layer)

30

The Proterozoic Eon (2.5-0.55Ga):
Transition to the modern world

- between 2.4 and 1.8 Ga ago large volumes of irons formations were deposited. These formation contain 90% of the world's mineable iron ore
- the period of formation of these deposits marks the transition between an atmosphere/ocean with little oxygen to an atmosphere with abundant oxygen (oxygen causes iron to precipitate --> form a solid)

31

The Proterozoic Eon (2.5-0.55Ga):
Transition to the modern world

- About 2 Ga ago eukaryotic cells appear (cells with a nucleus). Early forms were unicellular algae
- The appearance of eukaryotic cells (which photosynthesize more efficiently) led to a massive and rapid buildup of oxygen in the atmosphere, after 1.6 Ga ago.
- By 670 Ma complex shell-less invertebrates were inhabiting the seas (Ediacaran fauna)

32

The Phanerozoic Eon (545 Ma- present): visible life

- organisms with shells and bones evolved that are better preserved in the rock record.
- the past ~500 million years of the earth history has seen the diversification and increase in complexity of the life forms and major rearrangements of continental blocks

33

The Paleozoic Era (545 Ma -245 Ma)

- at the beginning of Cambrian, the continents were scattered, following break-up of the supercontinent Rodinia, about 750 Ma ago.
- Continents drifted during most of Paleozoic; towards the end of the era (Permian) continents were collected into a supercontinent called Pangaea

34

The Paleozoic Era (545 Ma -245 Ma)

- the beginning of Paleozoic coincided with the final part of the second major ice house. Gradual increase in plate tectonics activity led to high atmospheric CO2 levels, and as result warm greenhouse conditions were attained. During much of the Paleozoic Era the Earth as in a hot house.
- Paleozoic: time of inland seas and diversification of life (and organisms with shells and bones)
- during this period, first fish and first shark (check the time where they occurred)
- also check the time for first land plants, first amphibians and first reptiles

35

The Paleozoic Era (545 Ma -245 Ma) ended with the largest extinction event in the geological record (~250Ma)

- Permian -Triassic Extinction (PT boundary)
- marks the transition from the Paleozoic Era to the Mesozoic Era:
(1) greater than 90% of marine species lost
(2) greater than 70% of vertebrate land species lost
(3) only known mass extinction of insects as well (>50%)
- took earth a long time to recover (4-6 million of years)

36

The Mesozoic Era (245Ma-65Ma)

-Late Triassic: rifts formed and the Pangaea began to break up
- end of Jurassic (150 Ma ago): the Atlantic Ocean started to open
- end of Cretaceous (70Ma ago): most of present-day continents were separated, the Atlantic Ocean had formed, and India was moving rapidly northward
-for most of the Mesozoic the Earth had hot house conditions (~10C warmer than today). The atmospheric CO2 reached a maximum for the Mesozoic in late Cretaceous
- Mesozoic Era is the 'age of reptiles'
- first mammals occurred around 200Ma
- first birds (~160 Ma, evolved from flying dinosaurs)
- first flowering plants (~130Ma)

37

The Mesozoic Era (245Ma-65Ma) ended with a large extinction event (top 5) in the geological record (~65Ma)

- Cretaceous -tertiary extinction (KT boundary)
- marks the transition from the Mesozoic Era to the Cenozoic Era
(1) end of dinosaurs
(2) greater than 75% of all species lost

- KT extinction causes?
(1) Meteor impact
(2)Deccan Traps flood basalts
(3) probably both