Plate Tectonics and Boundaries

Plate Tectonics

• Plate tectonics is a theory unifying data about Earth's plate movement.
• Plates move on the mantle due to convection currents from the core.
• Technology confirms plate movement at centimeters per year.
• Plate tectonics explains Earth's changing surface.

Types of Plate Boundaries

• Plate boundaries are where tectonic plates interact.
• Three main types: convergent, divergent, transform.
• Convergent: Plates collide; subduction (one sinks) or collision occurs.
  • Oceanic plates sink beneath continental plates (denser).
  • Features: volcanoes, trenches, islands, mountains (e.g., Himalayas).
• Divergent: Plates move apart; new crust forms.
  • Features: mid-ocean ridges, rift valleys (e.g., Mid-Atlantic Ridge).
• Transform: Plates slide past each other; fault lines form.
  • Features: earthquakes due to pressure release (e.g., San Andreas Fault).

Landforms

• Landforms are Earth's physical features.
• Geomorphologists study how landforms change over time (internal: plate tectonics, volcanism; external: erosion, deposition, weathering).
• Common landforms: coast, island, peninsula, bay, mountain, hill, plateau, valley, canyon, plains.
• Ocean floor landforms: abyssal plains, valleys, seamounts, trenches, volcanic islands.

Solar System, Galaxies, and the Universe

• Solar System: Sun, planets (including moons), asteroids, dwarf planets, comets, meteoroids.
• Galaxy: Huge collection of gas, dust, stars, and solar systems, held by gravity.
• Universe: All of space, matter, energy, time, including planets, stars, galaxies. Large fraction is unknown dark matter.
• Universe contains hundreds of billions of galaxies in constant expansion.
• Galaxies have various shapes: spiral, elliptical, irregular.

Celestial Bodies

• Planets: significant gravitational pull, orbit a star, clear orbital path.
• Moons: orbit a planet.
• Asteroids: metal, rock, orbit the sun.
• Comets: icy bodies, have a gas tail as they near a star, orbit in an ellipse.
• Meteoroids: floating space rocks.
• Meteors: meteoroids entering Earth's atmosphere, burn up.
• Meteorites: meteors that reach Earth's surface.
• Terrestrial planets: solid surface, smaller, metal core (Mercury, Venus, Earth, Mars).
• Jovian planets (gas giants): no solid surface, composed largely of gases (Jupiter, Saturn, Uranus, Neptune).

Star Formation and Life Cycle

• Stars form in stellar nebulas (gas clouds).
• Protostar: first stage, hydrogen gas collapses, attempts core fusion.
• Brown dwarf: if protostar fails to accumulate enough mass for fusion.
• Main sequence: stable star, hydrogen fusion in core. Duration depends on star mass (10 million to 1 trillion years).
• Low-mass stars: become red giants, then planetary nebulae.
• High-mass stars: become red supergiants, then supernovae, leaving behind neutron stars or black holes.

Constellations and Star Clusters

• Constellations: groups of stars appearing close together in the sky (e.g., Cancer, Leo, Orion, Draco).
• Star clusters: physically close, gravitationally bound groups of stars. Formed together with galaxies, positions reflect early universe fluctuations.