Planetary Formation, Earth's Interior, and Plate Tectonics (Vocabulary)

Vocabulary flashcards covering key terms from the lecture notes on solar system formation, Earth's structure, and plate tectonics.

Planets in our solar system

The eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Terrestrial planets

Small, rocky, dense planets: Mercury, Venus, Earth, and Mars.

Jovian planets

Large, gaseous planets: Jupiter, Saturn, Uranus, and Neptune.

Solar nebula

A rotating cloud of gas and dust from which the solar system formed.

Inner region

Hotter part of the solar nebula where only rocks and metals condensed to form terrestrial planets.

Outer region

Colder part of the solar nebula where gases and ices condensed to form Jovian planets.

Gases

Hydrogen and helium; a category of planetary materials.

Ices

Water, methane, and ammonia ices.

Rocks/Metals

Silicates, iron, nickel; another category of planetary materials.

Accretion

Process of dust and particles sticking together to form planetesimals and eventually planets.

Planetesimals

Small solid bodies formed during accretion that combine to form planets.

Differentiation

Molten differentiation where dense materials sink to the core and lighter materials rise, creating core, mantle, and crust.

Core

Central, dense layer made primarily of iron-nickel.

Mantle

Middle layer of Earth composed mainly of silicate rocks.

Crust

Outermost solid shell; oceanic crust is basaltic, continental crust is granitic.

Direct evidence of Earth's composition

Evidence from rock samples, drilling projects, and volcanic eruptions.

Indirect evidence of Earth's composition

Evidence from seismic waves, Earth's magnetic field, and gravity measurements.

Inner core

Solid iron-nickel center of the Earth.

Outer core

Liquid iron-nickel surrounding the inner core.

Isostasy

Balance of Earth's crust floating on the denser mantle.

Oceanic crust

Thinner, denser, basaltic, younger crust.

Continental crust

Thicker, less dense, granitic, older crust.

Continental drift

Idea that continents were once connected and drifted apart; now explained by plate tectonics.

Pangea

The supercontinent about 250 million years ago.

Seafloor spreading

Formation of new crust at mid-ocean ridges and outward movement of the seafloor.

Mid-ocean ridge

Underwater ridge where seafloor spreading occurs.

Lithosphere

Rigid outer shell including the crust and upper mantle.

Asthenosphere

Weak, ductile part of the upper mantle on which tectonic plates float.

Plate tectonics

Theory that Earth's lithosphere is divided into plates that move.

Divergent boundary

Plates move apart; new crust formed at mid-ocean ridges.

Convergent boundary

Plates collide; crust destroyed in subduction zones and mountains form.

Transform boundary

Plates slide past one another; no crust creation or destruction.

Subduction zone

Where an oceanic plate sinks beneath another plate.

Collision zone

Where two continental plates collide, forming mountains.

Magnetic flips

Reversals of Earth's magnetic field; rocks record normal and reversed polarity.

Age of seafloor

Youngest rocks near mid-ocean ridges; progressively older farther away.

Magnetic stripes

Paleomagnetic stripes on either side of ridges that support seafloor spreading.

Seismic waves

Waves used to infer Earth's interior from changes in speed and path.