Astronomy EXAM 2 Review - Fall 2025

Earth’s Core is…

• Liquid & Solid

• Spins

• Hot

Earth’s mantle is…

solid & thick

earth is composed of what 4-5 parts?

inner core, outer core, mantle, crust, & atmosphere

our magnetic field protects us from…

solar winds by deflecting the charged particles

where do the charged particles get diverted to?

to the earth’s poles, where they crash into the particles in our atmosphere, causing the aurora borealis, where they are ONLY found

the earths magebitic dynamo is caused by the combination of..

…the convection in the earth’s molten core and the earth’s daily rotation.

liquid metal in the outer core that generated electrical currents, and the rotation of earth on its axis causes said currents to form a magnetic field

igneous rocks

solidified from cooling magma / lava

ex: basalt, granite

sedimentary rocks

formed from compressed or cemented layers of sediment such as sand, mud, or even shells

ex: sandstone, limestone

metamorphic rocks

created through the transformation of existing rocks through heat, pressure, or shemical changes without melting

ex: marble

5 Key Evidence pieces for continental drift

1. fit of the continents

2. fossil correlation

3. rock formations / mountain ranges

4. earthquake and volcano distribution

5. direct GPS measurements (direct data shows continents moving a few centimeters a year)

The theory of plate tectonics explains..

how slow motions within the mantle of earth moved large segments of earth’s crust

composite volcanoes

thick lava, 900 F, peaky and deadly as pressure builds up causing a violent explosion

ex: mount rainier

shield volcanoes

thin and runny lava, 2200 F, soft and wide spread volcanoes, less-violent eruptions as pressure does not build up

ex: mount kea

occurs when an oceanic plate is pushed under a continental plate

mountain ranges, composite volcanoes

occurs when two oceanic plates collide and one gets pushed under the other

a chain of islands are created out of volcanoes that pop up

hotspot

occurs when a weak spot in the asthenosphere and lithosphere lets magma flow to the oceanic or continental crust

a chain of volcanoes are formed when..

the plate is moving

what geological feature does not necessarily indicate that a planet has plate tectonic activity

an isolated shield volcano as they are formed out of hotspots, which are not convergence points between tectonic plates

the age of the sun is ____ compared to the earth

basically the same age within a few million years

charles darwin thought that

the earth had to be atleast hundreds of millions years old to allow for gradual evolution of species

Most people at the time of Charles Darwin thought that the earth was 6000 years old due to..

biblical interpretations

lord kelvin thought that the sun could only be

20-40 million years old

why did lord kelvin think the sun was only 20-40 million years old

The sun cannot be eternal, as it would violate thermodynamics

• the sun is burning some internal fuel, which would eventually run out (nuclear fission),

• the sun is continuously supplied with energy from an external source

• the sun was the hottest when it was formed and has slowly been cooling off over time

the best estimates for the age of the earth AT THE TIME from ?????

erosion dating

what processes regulate energy coming in to earth

sunlight, tidal friction, residual heat from the earths formation, and radioactive decay of elements inside of the earth

As the earth’s surface absorbs energy from the sunlight and its interior, what is the best evidence that it radiates nearly the same amount of energy back into space?

the fact that the earth’s surface temp is not changing much (aka similar every year)

how much heat still eminates from the earth’s interior today from its initial formation

22 terrawatts of heat = 2,000,000,000,000

radioactive decay processes are when

unstable atoms break apart or transform

the interior of the earth keeps itself warm through

the radioactive decay of unstable elements

uranium and thorium atoms break apart to make

lead

potassium atoms break apart to create

calcium and argon

radioactive decay

a process in which unstable atoms break apart

if the process of radioactive decay transforms an element into a diff element by breaking it apart, it is called

nuclear fission

percentage of the earth’s internal energy production associated with radioactive decay

44% thorium

41% uranium

15% potassium

if thorium has a half life of 14 billion years, then that means

that every 14 billion years, half of the thorium 232 you intially had will be gone as it has broken apart to become a lighter element

we get roughly the same amount of energy from the sun all year round, and it is always hitting half of the earth

true

how much energy is continuously hitting earth from the sun

173,000 terrawatts = 173,000,000,000,000,000 watts

friction between the ocean and its floor causes

its rotational energy to dissipate, causing the oceans to warm slightly

nearly 30% of tidal energy is dissipated in

deep oceans that help sustain deep ocean currents

in the middle of the ocean it typically rises to 2 feet. on land, it can rise an entire foot

true

earth also causes tidal effects on the moon, causing its surface to rise by

4 inches

the sun causes tidal effects on the earth but its contribution is ____ of the moon’s

less than half

tides between the earth, sun and the moon cause enough friction to heat the earth by…

3.7 terrawatts = 3,700,000,000,000

energy reaching the earth’s surface conclusion

sunlight: 173,000 terrawatts

radioactive decay: 24 terrawatts

residual formation heat: 22 terrawatts

tidal friction: 3.7 terrawatts

what percentage of the energy that reaches the Earth’s surface does sunlight supply?

99.97%

based on the energy reaching the surface of the earth, earth’s average temperature should be

40.3 F

earths actual temp avg is

58.6 F

reflection

hinders energy from being absorbed by the earh’s surface

oceans reflect ___ of UV light, and ___ of all colors of light

7% / 6%

dry beach sand reflects ___ of UV light, and ___ of all colors of light

17% / 45%

snow reflects ____ of UV light, and ___ of all colors of light

88% / 95%

old snow reflects ___ of UV light, and ___ of all colors of light

50% / 75%

weather

changes in temp, humidity, and precipitation on SHORT time scales (mins, hours, days weeks)

climate

the average temp humidity and precipitation on a LONG time scale (10 or more years)

the earth is currently experiencing 

a rapid period of warming due to climate change

warmer + wetter =

more growth

colder + drier =

less growth

what can be utilized by scientists to detect temperature of a past period

trees and their rings

• they can live for hundreds of thousands of years

• growth rate is correlated to temp

• can be burnt down and correlated with the growing temps that the tree experienced in its life

the average global temp has risen by ____ since 1880 / since the twentienth century with significant warming towards the poles than in the equatorial region

1.7%

warming leads to extreme general weather such as

hurricanes, wildfires, heat waves & droughts: become frequent and more intensive

cold waves: shorter and less frequent

flood patters: change as precipitation may come all at once

over the last 122,000 years / 20,000 years, ice isn the artic and antartic has gotten

thinner, as it is melting at an unprecedented rate. this affects sea levels and animal migration patters

global sea levels have risen roughly ___ since 1880

8 inches

global sea levels are projected to rise ___ by 2100

another 1 to 4 feet

earths orbit around the sun is nearly circular, its distance only changing by how much during the year?

by about 3.3% during the year, causing a 7% variation in the heat we receive during the year

we are MOVING AWAY from the sun at a rate of

5ft per century, meaning that our orbit will grow by 0.01% in 1 billion years

how often does the sun’s magnetic field flip, switching the north and south poles?

every 11 years

the avg surface temp of the sun is

10,000 F

sunspots avg temp is

6,400 F

strong magnetic fields surpress the release of heat into the photosphere, making

sunspots cooler

during the solar cycle of 1996-2006, the solar maximum occurred during ___ and the solar minimum occurred during ___

2001 ; 1996/2006

in the 10,000 years before the industrial revolution in 1751, CO2 levels rose less than 1%. Since then they’ve risen by

43%

80% of human produced CO2 comes from

burning gasoline, natural gas, oil, and gasoline

since humans produce more than 37 billion tons of CO2 a year, where does it all go?

40-50% lingers in the atmosphere, 30% is dissolved into the oceans, and scientists are unsure about the rest. they believe it is absorbed by forests, soil, and crops

the atmosphere accounts for ___ of the earths mass

0.0001%

earth’s surface reemits sunlight / the sun’s energy as

infrared lightsome escapes into space, some bounces off the atmo and back to the surface of the earth

the greenhouse effect is caused mostly by ___ in the atmosphere

large molecules that absorb light and reemit it as infrared light in every direction, trapping some of the energy trying to escape the earth

examples of greenhouse gases

CO2, N2O, H20, O2, CH4

carbon and nitrous dioxide, water, oxygen, methane

carbon dioxide c02

• primary greenhouse gas

• responsible for 75% of emissions

• can linger in atmo for thousands of years

• emissions mainly come from the burning of organic materials such as coal, gas, wood, and solid waste

methane CH4

• accounts for 16% of all greenhouse gas emissions

• stays in atmo for 12 YEARS

• released from landfills, natural gas and petroleum industries, and agriculture (digestive systems of animals)

• levels have increased by 84 TIMES over the last two decades

nitrous oxide (N2O)

• 6% of all greenhouse emissions

• lifetime in atmo exceeds a CENTURY

• produced by agriculture, livestock, and burning fuel (fertilizer, manure, the burning of agricultural residues)

main source of heat that warms up the earth’s atmo

sunlight

main source of heat that warms up the moon’s surface

sunlight; no greenhouse effect as moon has no atmo

because the moon orbits the sun, its average distance from the sun is the same as

the earth’s

oceanic subdued by continental

deadly composite volcanoes form in a mountain range

continental subdued by continental

no volcanoes, but a mountain range is formed

oceanic subdued by oceanic

produces shield volcanoes that form into islands

charles darwin estimated that erosion alone would require the earth to be more than ____ years old. Lord Kelvin argued that one cannot use a steady rate of erosion, and accounting for so would decrease the earth’s age

300 million

lord kelvin reasoned that

the earth could have formed out of a molten ball of rock that had cooled off enough to explain its hardened crust

LK estimated that the earth was originally ____ which would require between 20-40 million years to cool to its current state

7000 F

earth is estimated to be about ____ million years old through radioactive dating

4.5 million years old

LK underestimated the age of the sun because

he did not know its energy came form nuclear fission

geologists underestimated the age of the earth because

carbon dating was not yet accurate / radioactive dating was in its infancy & erosion models were too simple / unproperly accounted for

what do we use to determine the age of the earth

radioactive dating

radioactive decay

the process in which unstable atoms break apart / transform

earths core continues to generate heat because of

radioactivity. when the particles decay, they release energy that heats up their surroundings

the earths core is hot due to

residual heat from its formation, and radioactivity

list the earth from top to bottom twin

exo, thermo, meso, strato, tropo, crust, u.mantle, l.mantle, o.core, i.core

the oceans, land, and ice reflect ___ of the light back into space, causing a reduction in the expected avg temp to 17.6 F

17%

60% of the earth is covered by clouds, which reflect another 13% of the light, lowering it ???? to

-2.3 F

expected avg surface temp based on energy sources and light reflection is

-2.3 F