The fact that Earth is geologically active means…
It’s surface is constantly being reshaped be volcanic eruptions, earthquakes, erosion, etc
Interior structure
1) core - the highest density - in the center
2) mantle - rocky materials of moderate density - around the core
3) crust - the lowest density - visual part - forms the outer skin
+ lithosphere - Earth outer layer of cool and rigid rock (crust + upper layers of mantle)
Differentiation
- a process by which gravity separates materials according to their density, with high density material sinking and low density materials rising—> multiple interior layers
Why terrestrial planets were once hot enough to melt materials to form layers?
1) after accretion Ep transformed into E(thermal)
2) radioactive decay released heat directly into a planetary interior, converting mass-energy (E=m*c) into E(thermal)
Convection
The energy transport process in which warm materials expands and rises while cooler materials contracts and falls (happens very slow)
How it happens: core releases heat that melts lower mantle, makes the material less dense -> it rises —> cycle
—> Magnetic field —> magnetosphere (— the region surrounding a planetary interior in which charged particles are trapped by the planet’s magnetic field (exists due to convection)) —> protects Earth shielding it from solar wind
What processes shape Earth’s surface?
1)impact cratering
2) volcanism - the eruption of molten rock (lava) from its interior to the surface — volcanic outgassing formed atmosphere and ocean
HOW: during Earth’s formation -> accretion -> rock, water and gas trapped beneath the surface -> later some were released by volcanic eruption
3) tectonics (esp planet tectonics) — disruption of a planet’s surface by interior stresses
2-3 require internal heating and therefore depend on a planet’s size
4) erosion — the wearing down and building up of geological features by water, wind, rain, snow and other phenomena of planetary weather
How does Earth’s atmosphere affect the planet?
1) greenhouse effect —> warm temperatures + water stays liquid
2) surface protection from solar radiation by absorbing X-rays in high atmosphere and ultraviolet light in the middle of atmosphere by ozone. Only visible light reaches the ground (blue light is scattered => blue color of the sky), and than remitted as infrared light
The Moon’s geographic features
— the moon’s dark, smooth Maria - lava flooded craters later after they were formed when the Moon’s interior were heat by the radioactive decay
— has water ice (from impacts from comets) (very little)
— NOW geologically dead
Mercury geological features
— NOW geologically dead (small size)
— some crater floors appear to release easily vaporized materials from the rock, causing the rock to crumble and make “hollows”
— the release of easily vaporized gases leaves behind a light-colored coating whose composition remains unknown
— water ice in permanently shadowed craters near Mercury’s poles (from impacts from comets)
— has a set of tremendous cliffs all over its surface (probably formed when tectonic forces compressed crust, causing the surface to crumble ==>==> Mercury appears to have shrunk long ago, leaving behind long, steep cliffs)
Mars
— has frozen
— more elliptical => more extreme seasons
— thin atmosphere => weakened greenhouse effect => cold
— geological evidence of past water flows: river bends/ lake bends, indistinct rims of many large craters and lack of small craters (erosed)
—the dramatic difference in Mars’s terrain around different parts of the planet
— past volcanism -> dotted with many volcanoes
Why did Mars froze?
Apparently Mars must have somehow lost its carbon dioxide (hypothesis: due to change in its magnetic field) -> weakened greenhouse effect -> lower t until the planet frozen over
+ small proportion of carbon dioxide condensed forming ice caps of Mars’s poles (polar caps) (the majority was lost in space)
Venus
— similar in size and composition to Earth but different in other ways
— geologically active
— very strong greenhouse effect — b/c of thick carbon-dioxide atmosphere — somehow lost its outgassing water (from volcanism activity) leaving carbon dioxide (hypothesis: its evaporated b/c Venus is closer to the Sun) **— gases are trapped within atmosphere—> very-very hot
— shows features of volcanism and tectonics
— no erosion b/c too hot for water and snow/ rain AND too slow (rotation) for wind and weather
— absence of planet tectonic. Instead surface is all the same age on Venus (hypothesis: b/s Venus has a thicker and stronger lithosphere)
**Earth has as much carbon dioxide but because it is mostly locked in rocks rather than in our atmosphere, we don’t have that bizarre greenhouse effect)
What unique features of Earth make it habitable?
1– surface liquid water
2– atmospheric oxygen — from photosynthesis
3– plate tectonics — act like a giant conveyor belt for Earth’s lithosphere, recycling the sea floor and building the continents (-> subduction (zones))
4– stable climate — the process of Earth self-regulating its t — carbon dioxide (CO2) cycle - the process that cycles carbon dioxide between Earth’s atmosphere and surface rock
The higher⬆️ the t = the higher⬆️ rate at which carbon dioxide is removed
Carbon dioxide cycle (=CO2 cycle)
- the process that cycles carbon dioxide between Earth’s atmosphere and surface rock
That’s how Earth self-regulates its t ensuring stable climate
The consequences of climate change
1- ⬆️t -> ⬆️E(total) available-> ⬆️more frequent extreme weather events
2- ⬆️⬆️the level of ocean
3- ocean more acidic
