midterm exam for universe part 4

How does the plate tectonics work? What is required for the plate tectonics to work? (Although we clearly know that the heat in the center of the Earth is the main cause, we cannot deny the fact that the water is equally important for the plate tectonics to work.)

• Heat from the core creates convection currents in the mantle.

• Water plays a key role by lubricating plate movement and weakening the lithosphere, making subduction easier.

What is a subduction zone, divergent boundary, rift zones, fault zones, hotspots?

• Subduction zone: A denser oceanic plate sinks beneath a lighter continental plate, forming trenches & volcanoes.

• Divergent boundary: Plates move apart, creating new crust (e.g., Mid-Atlantic Ridge).

• Rift zones: A specific type of divergent boundary where a continent splits, forming valleys (e.g., East African Rift).

• Fault zones: Regions where plates slide past each other, causing earthquakes (e.g., San Andreas Fault).

• Hotspots: Areas where magma rises from deep mantle, forming islands (e.g., Hawaii).

How are mountains formed?

• Collision of tectonic plates (e.g., Himalayas formed from India colliding with Eurasia).

• Volcanic activity (e.g., Andes Mountains).

• Uplift from faulting (e.g., Sierra Nevada).

What does the nebular theory explain?

It explains how the Solar System formed from a rotating cloud of gas and dust (solar nebula).

What is a frost line in a nebular theory?

The distance from the Sun where it was cold enough for ices (water, ammonia, methane) to condense into solid form.

What is a nebular theory? Go over the steps of the nebular theory

• Step 1: A cloud of gas & dust collapses due to gravity.

• Step 2: The cloud spins faster, forming a flat disk.

• Step 3: The Sun forms at the center; dust particles stick together forming planets.

• Step 4: Rocky planets form near the Sun; gas giants form beyond the frost line.

• Step 5: Solar winds clear remaining gas & dust, leaving behind the Solar System.

What are inner planets? What are outer planets? Practice writing them in the right order.

• Inner planets (terrestrial, rocky): Mercury, Venus, Earth, Mars

• Outer planets (gas/ice giants): Jupiter, Saturn, Uranus, Neptune

What are dwarf planets? How many we got in the solar system?

Dwarf planets are small celestial bodies that orbit the Sun but haven't cleared their orbit.

• Five official: Pluto, Eris, Haumea, Makemake, Ceres

Is Pluto a planet or a dwarf planet?

Dwarf planet

Why do all the planets rotate in the same direction? (Explain using Nebular theory)

Because they formed from a rotating disk of gas and dust, all planets inherited the same direction of motion.

Why do most of the planets spin in the same direction? (Explain using Nebular theory)

The original angular momentum of the spinning nebula caused the planets to rotate in the same direction.

Why do all the planets lie in a plane? (Explain using Nebular theory)

As the solar nebula spun, it flattened into a disk, so planets formed within that plane.

Why do the planets close to the Sun are rocky?

Near the Sun, it's too hot for gases and ices to condense, so only metals and rocks could form planets.

Why are Jovian planets made up of Hydrogen mostly?

Beyond the frost line, temperatures were low enough for gases like hydrogen and helium to accumulate.

More the craters on the surface of a planet, …………………. (older/newer) is the planet surface.

Older