Midterm 1 content Flashcards
(31 cards)
Define impact aggregation
The formation of planetary bodies after an impact such as the condensation of dust/gas around the protosun after the Big Bang and the collapse of a nebula formed the solar system.
Define hemispheric dichotomy
Specifically on Mars, a large impact caused the North to have a lower elevation than the South.
Define the Giant Impact Hypothesis.
Theoretically, a planet the size of mars called Theia crashed into Earth. This giant impact resulted in a lot of debris and intense heat which knocked Earth off its axis. The debris then collects as it orbits the Earth which then forms the moon (impact aggregation). This is also why similar isotopes are found on the Earth and the Moon.
Define a synestia.
A donut-shaped “soup” of dust and debris that forms from impact debris in a fast-spinning vaporized state after a giant impact (ex. the earth after being hit by theia). The synestia then cools and condenses to form the moon within the synestia. As the moon contracts, it forms its own orbit.
Define LHB
Late Heavy Bombardment (3.5-4.0/4.2 Ga) - a period of time in which a significant amount of violent activity from asteroids and comets occurred. Evidence of this is seen on the moon and Mars where no plate tectonics is able to “recycle” the scars. This may have been caused by the alignment of orbits which pulled objects into the inner solar system.
What 3 things resulted in the leading hypothesis for where water originated?
- Comet impacts (water vapour found in the stars)
- Volcanism- molten magma has many dissolved gases (H2O (g)) which is released via volcanic eruption
- Asteroids - the water is chemically bound to the asteroid’s formation and can only be released by breaking these bonds (by heat)
Define BIF and what they were indicators of.
The Banded Iron Formations acted as evidence of when water was first present on Earth (3.8 Ga). Iron-rich stratified rocks that used to be soft precipitative material which collected at the bottom of the oceans, the iron in the water came from volcanic eruptions . Cyanobacteria is needed to produce oxygen in the water to react with the iron which forms layers which is then compressed over time to form rock.
How did Earth get its atmosphere?
- First atmosphere made of hydrogen, water vapour, methane and ammonia.
- Products of volcanism (nitrogen, CO2, inert gases) supplemented by the gases released from asteroid impacts
- GOE= great oxygenic event (2.3 Ga) which was an increase in oxygen levels bc the dissolved iron was used up in chemical reactions so leftover oxygen was released into the atmosphere
What conditions do electromagnetic radiation (EM) need to be emitted and what does it depend on?
It must be above a temperature of absolute zero and depends on Lsun (luminosity of the sun=energy multiplied by area) and d (the distance between the Earth and the Sun) which results in solar constant (Sc).
Define the Goldilocks Principle.
Earth needs to be “just right.”
- In the search for another habitable planet, liquid water must be present and it must be a safe distance from a star
“The Habitable zone”
- You need to know the star’s mass (related to luminosity) to calculate distance (AU) to the proximal/distal bounds of the habitable zone
Define radiating level
Lowest level in the atmosphere from which IR is able to escape to outer space without being absorbed. The greater the concentration of greenhouse gases in the atmosphere, the higher the radiating level. If there were no greenhouse gases or clouds, the radiating level would be at the Earth surface.
- Stays the same while greenhouse gases push this higher into the atmosphere
- Radiating level rises hundred of meters per every couple of degrees
Lapse rate = 6.5 degrees Celsius per km
Define Apsides
extreme points in the orbit of a planet around a star (Earth around the Sun)
- Closer to the sun in the winter
1) Perihelion (Jan. 3, 2019)
peri = close, helion = the sun
2) Aphelion (July 4, 2019)
ap= farthest from, helion = the sun
• The dates of the apsides change over time due to Milankovitch cycles
Define solstices
the longest and shortest days of the year in either hemisphere
- Summer solstice (June 21) = guaranteed 24 hours of sunlight in the north - receives higher energy flux - Tropic of Cancer (23.44 degrees North) - on the summer solstice it is 90 degrees to the sun - Winter solstice (December 21) = shortest day - the solar angle at noon is 43.12 degrees - receives a lower energy flux (can be calculated) *Northern hemisphere has longer solar angle/hours in the summer vs. The winter solstice The southern hemisphere has shorter solar angle/hours in the summer vs. The winter solstice
Define Equinoxes
The time in which the equator at either equinox (autumnal or vernal) there will be a 90 degree solar angle
• At the equator, highest TOA (top of atmosphere) occurs in the spring/fall (at the equinoxes), not in the summer
• You see a drop in the equator in the summer bc of one of the tropics
*Nothing changes in terms of solar hours at the equinox (about 12 hours at both equinoxes)
Why is the ozone hole so pronounced in polar regions?
- BC we emit a lot of chemicals into the atmosphere
- CFCs and halons have a long lifetime in the atmosphere which does not react to anything which then makes way to the polar regions
- From CFCs, a chlorine atom is released which then destroys thousands of ozone molecules- leads to ozone hole
- Polar vortices = build up of pollutants which develops over winter and forms an atmospheric container of cold air
- Stratospheric clouds form- Provides a surface for chlorine to transform into ozone-destroying form which then occurs in Spring
- Ozone is destroyed in spring with increased sunlight
Define sources, reservoirs and sinks. Give an example of each.
A source is where/how something enters a reservoir (ex.respiration, combustion)
A reservoir is where that substance is stored (ex. the atmosphere)
A sink is where/how something is removed from a reservoir (ex. a tree is a good sink for carbon)
Slow CC
slow carbon cycle where CO2 is emitted into the atmosphere through volcanic eruptions
- Occurs over hundreds of millions of years * oceanic crust is more dense and subducts before melting again which then transfers out through volcanic eruptions - Geologic time- scale (biogeochemical cycle) associated w organic and inorganic
Ex. Ground critters (gophers) dig up tunnels/mounds resulting in the bioturbation of soil carbon which is then returned to the atmosphere
- Bc of human activity entering the oceans, the ocean temperatures are rising
Where does the OH radical come from?
Ozone reacts with UV light creating a diatomic oxygen and an oxygen atom.
The oxygen atom (O) reacts with water vapour to form 2 OH radicals.
What are the 3 elements of climate change?
- Magnitude = how big is the change (delta)
- What is the difference from some long term average - Frequency = how often are extreme events (ex. Hurricanes can be more powerful and earthquakes)
- Duration = how long do events last? (ex. Heatwaves, droughts)
- Hurricane dorian stalled at the coast
What effect does climate change have on weather events?
climate change is not the cause of extreme weather events its simply affected by it bc the environment in which they occur is warmer/moister than it used to be (1 degree Celsius increase= 7% increase of moisture)
It also increases the probability/magnitude of some extreme weather events (rainfall, flooding, wildfires, droughts, extreme heat spells)
Why does climate change occur?
- Variations in the sun’s energy reaching earth
- Maunder minimum (the period when sunspots were especially rare)
- The earth-sun geometry is not constant (Milankovitch Theory)
- Eccentricity changes the extreme temperatures on Earth by changing its elipticity around the sun - affects luminosity, TOA, Sc
- Tilt and precession has more of an effect on the seasons
- Changes in the reflectivity of earth’s atmosphere and surface (albedo = 30% reflectivity- this value is not constant bc in the Ice Age it had a higher reflectivity (more white surfaces))
- TOA (341) * 0.7 = 238.7 Wm^-2
- 0.7=absorbtivity - **what happens to the resulting value when this changes - Changes in the greenhouse effect which affects the amount of heat retained by Earth’s atmosphere
What is the difference between radiating and actual temperature for the planets? What explains the large difference on Venus and the small difference on Mars?
Venus is closest to the sun (smallest AU) while Mar is farthest from the sun (larger AU). Since being closer to the sun warms the planetary body, it loses energy to space by IR making the radiating temperature significantly different from the actual temperature of Venus.
Define geopotential height.
The height in km of the 500 mb surface.
how high you need to go before reaching a pressure of 500 mb
Describe a thermal low pressure system vs. a thermal high pressure system.
When the air warms, it rises and the surface beneath it decreases in pressure.
When the air cools, it sinks and causes the surface to increase in pressure.
