CSET Earth and Space Science: General Science Domain 4

Big Bang & Evidence

• Big Bang Theory

  • The universe began in an extremely hot, dense state and has been expanding.

• Cosmic Expansion

  • Galaxies are generally moving away from each other.

  • Hubble’s Law

• Cosmic Microwave Background (CMB)

  • Leftover radiation from the early universe.

  • The leftover heat from the big bang

• Redshift

  • Light from distant galaxies is shifted toward longer wavelengths (red), showing they are moving away from us.

Astronomy & Astronomical Instruments

• Astronomy is the study of objects and phenomena in space.

• Telescope

  • Collects electromagnetic radiation to observe distant objects.

• Optical Telescope

  • Detects visible light.

• Radio Telescope

  • Detects radio waves.

• Space Telescope

  • Observes from above Earth's atmosphere, avoiding atmospheric interference.

• Spectroscope / Spectrometer

  • Separates light into its wavelengths to study stellar spectra.

Stars

• A massive ball of hot gas/plasma that produces energy and light.

  • The Core is where nuclear fusion occurs.

• A star’s mass determines its temperature, brightness, lifespan, and evolution.

• More massive stars → hotter, brighter, shorter-lived.

• Less massive stars → cooler, dimmer, longer-lived.

• Star Life Cycle:

  • Nebula → A giant cloud of gas and dust in space where gravity starts to pull particles together.

  • Protostar → A dense, hot ball formed as the gas collapses, but before nuclear reactions start.

  • Main Sequence → The longest, most stable phase in a star’s lifetime

  • Deep inside the core, extreme heat and pressure force tiny hydrogen atoms together to make helium.

  • It releases a huge amount of energy as light and heat.

Stellar Spectra

• Spectrum → range of wavelengths of light.

• Spectral lines → specific wavelengths absorbed or emitted by elements.

• Each element has a unique spectral fingerprint.

  • Scientists use spectra to determine a star’s:

    • Composition

    • Temperature

    • Motion

• Redshift → spectral lines shift toward red → object moving away.

• Blueshift → spectral lines shift toward blue → object moving toward.

Solar System

• Solar system → the Sun and all objects that orbit it.

• Gravity keeps planets and other objects in orbit around the Sun.

• Orbit is the path an object follows around another object.

• The Sun is a star and contains most of the solar system's mass.

  • Inner planets: Mercury, Venus, Earth, Mars → small and rocky.

  • Outer planets: Jupiter, Saturn, Uranus, Neptune → much larger.

• Planets orbit the Sun and rotate on their axes.
  
  

• Rotation → day/night

  • The side facing the Sun receives sunlight → day 

  • The side facing away from the Sun is in darkness → night

• One full orbit around Sun = year

Milky Way

• Galaxy 

  • A huge collection of stars, gas, dust, and other matter held together by gravity.
    
    

• The Milky Way is the galaxy that contains our solar system.

• Spiral galaxy = a galaxy with a central region and curved spiral arms.

  • The Milky Way is a spiral galaxy.

  • Our solar system is located in one of those spiral arms.

• The Milky Way is much larger than our solar system.

  • Universe → Galaxy → Solar System → Earth

Formation/History of Earth

• Phase 1: The Solar Nebula (Solar System Formation)

  • The Cloud: A massive cloud of gas and dust (solar nebula) collapses due to gravity.

  • The Sun: Gravity pulls 99% of the material to the center, igniting the Sun.

  • The Disk: The remaining 1% of material flattens into a spinning protoplanetary disk.

• Phase 2: Accretion and Differentiation (Earth Formation)

  • Accretion: About 4.6 billion years ago, dust and rocks collided and stuck together, growing into Earth.

  • Melting: Continuous space collisions and radioactive decay generated extreme heat, melting early Earth.

  • Differentiation: Gravity separates the molten Earth by density. Heavy metals (iron, nickel) sink to form the core; lighter rocks float to form the mantle and crust.

  • Cooling: Earth slowly cools, forming a solid crust and allowing water vapor to condense into oceans.

Uniformitarianism vs. Catastrophism

• Uniformitarianism

  • The idea that the same geological processes happening today also happened in the past.

    • Example:

      • erosion slowly shaping land today → erosion also shaped land in the past

• Catastrophism

  • The idea that sudden, major events can cause large changes to Earth.

    • Examples: 

      • asteroid impacts, volcanic eruptions, earthquakes.

Seasons, Eclipses, and Tides

• Seasons

  • Earth’s axis is tilted 23.5°.

  • As Earth orbits the Sun, that tilt causes each hemisphere to receive different amounts and angles of sunlight.

    • Tilted toward Sun → summer (more direct sunlight + longer days)

    • Tilted away → winter (less direct sunlight + shorter days)

  • Northern and Southern Hemisphere seasons are opposite.

• Eclipses

  • Occurs when one celestial body moves into the shadow of another.

    • Solar eclipse = Moon between Sun and Earth → Moon's shadow falls on Earth.

    • Lunar eclipse = Earth between Sun and Moon → Earth's shadow falls on Moon.

• Tides 

  • The regular rise and fall of ocean levels, caused mainly by the Moon's gravity.

  • The Moon's gravity pulls on Earth's oceans, creating high and low tides.

Seismic Waves

• Waves of energy produced by earthquakes or other movements in Earth's crust.

• P-waves (primary)

  • Fastest seismic waves; compressional; can travel through solids and liquids.

  • P-waves arrive first because they travel faster.

• S-waves (secondary)

  • Slower than P-waves; transverse/shearing; can travel through solids only.

  • S-waves arrive second.

• Scientists use the behavior of P- and S-waves to learn about Earth's interior.

• S-waves cannot travel through Earth's liquid outer core, which provides evidence that the outer core is liquid.

Minerals

• Naturally occurring: forms through natural processes, not manufactured by humans.

• Inorganic: not made by living organisms or derived from living matter.

• Solid: has a definite solid form.

• Definite chemical composition: made of specific elements in a specific chemical ratio.

• Ordered crystalline structure: atoms are arranged in an organized, repeating pattern.
  
  

• Minerals can be identified using physical properties:

  • Color → what it looks like, but not always reliable.

  • Streak → color of the mineral’s powder.

  • Luster → how the surface reflects light (metallic, glassy, dull, etc.).

  • Hardness → resistance to scratching.

    • Measured using the Mohs hardness scale (1–10).

    • Talc = 1, diamond = 10.

Rocks

• A naturally occurring solid made of one or more minerals.

• Unlike minerals, rocks do not necessarily have a specific chemical composition.

• 1. Igneous

  • Form when magma or lava cools and solidifies.

  • Intrusive → cools underground → slow cooling → larger crystals.

  • Extrusive → cools at Earth's surface → fast cooling → smaller crystals.

• 2. Sedimentary

  • Form when sediments are deposited, compacted, and cemented.

  • Often form in layers.

  • Can contain fossils.

    • Example: sandstone, limestone.

• 3. Metamorphic

  • Existing rock changed by heat, pressure, or chemically active fluids.

  • Does not completely melt.

    • Example: limestone → marble; shale → slate.

Weathering

• The breakdown of rocks at or near Earth's surface.

• Mechanical (Physical) Weathering

  • Breaks rock into smaller pieces without changing its chemical composition.

  • Examples:

    • Ice wedging: water enters cracks, freezes, expands, and breaks rock.

    • Abrasion: rocks/sediment scrape against each other.

    • Temperature changes: repeated heating/cooling causes expansion and contraction.

    • Plant roots: roots grow into cracks and force them wider.

• Rock gets smaller, but stays chemically the same.

• Chemical Weathering

  • Changes the chemical composition of the minerals in a rock.

  • Examples:

    • Water dissolving minerals

    • Acid rain reacting with rock

    • Oxidation — oxygen reacts with minerals, like iron rusting

Erosion & Deposition

• Erosion 

  • The natural process where earth, rock, and soil are worn away and moved to new places by forces like water, wind, or ice

• Causes of Erosion

  • Water → rivers, streams, waves, runoff

  • Wind → moves sand and small particles

  • Ice → glaciers move rocks and sediment

  • Gravity → causes landslides and rockfalls

• Deposition

  • When transported sediment is dropped/settles in a new location

• Weathering → Erosion → Deposition

Relative Dating

• Relative Dating

  • Determines whether something is older or younger than something else.

  • Tells you the order of geological events, not the exact age.
    
    

• Law of Superposition

  • In undisturbed rock layers, oldest layers are on the bottom and youngest are on top.

• Original Horizontality

  • Sedimentary layers are originally deposited horizontally.

• Cross-cutting relationships

  • A rock or fault that cuts through another rock is younger than the rock it cuts.

• Inclusions

  • Pieces of rock contained inside another rock are older than the rock containing them.

• Faunal succession

  • Scientists use fossil patterns to identify and compare the ages of rock layers.

Absolute Dating

• Absolute Dating:

  • Determines an actual numerical age of a rock, fossil, or event.

• Radiometric Dating:

  • A type of absolute dating that determines the absolute age of a rock or fossil by measuring the predictable decay of radioactive isotopes.

• Use of Isotopes:

  • A radioactive parent isotope naturally decays into a daughter isotope at a known rate (half-life).

  • Using the isotope's known half-life, they calculate the age of the sample.

• Carbon 14:

  • Living things continually exchange carbon with the environment, so while alive their C-14/C-12 ratio is approximately the same as the environment.

  • Scientists can measure that ratio in living organisms today and use it as the starting point.

  • Comparing the current C-14/C-12 ratio to the known starting ratio tells scientists how much C-14 has decayed → therefore, how long ago it died.

Geologic time

• The enormous span of Earth's history, from Earth's formation about 4.6 billion years ago to today.

• Eon → Era → Period → Epoch

• Major Eras

  • Paleozoic

    • "Ancient life"

    • Marine life became abundant

    • Plants and animals began colonizing land

    • Ends with the Permian mass extinction

    
    

  • Mesozoic

    • "Middle life"

    • Often called the Age of Reptiles

    • Dinosaurs were dominant

    • Ends with the mass extinction that eliminated non-avian dinosaurs

  
  

  • Cenozoic

    • "Recent life"

    • Mammals became much more prominent

    • Includes the period in which humans evolved

Earth’s Energy Systems

• Solar energy

  • Energy from the Sun

  • Drives weather, climate, evaporation, water cycle, photosynthesis.

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• Geothermal energy 

  • Heat from inside Earth; drives many geological processes.

  • Drives plate tectonics,  earthquakes, volcanoes, mountains.

Evidence for Plate Tectonics

• Continental fit → continents like South America and Africa appear to fit together.

• Matching fossils → same fossils found on continents now separated by oceans.

• Matching rocks & mountain ranges → similar rock formations occur on different continents.

• Seafloor spreading → new oceanic crust forms at mid-ocean ridges.

• Magnetic stripes → symmetrical magnetic patterns on both sides of mid-ocean ridges show that new crust formed and moved outward.

• Earthquake & volcano patterns → they occur in predictable zones that correspond to plate boundaries.

Plate Boundaries

• Divergent: 

  • Plates move apart → magma rises → magma cools → new crust forms

  • Example: mid-ocean ridges

• Convergent 

  • Two plates move toward each other

  • Oceanic + Continental → subduction

    • The denser oceanic plate sinks underneath the continental plate.

    • This can cause earthquakes and volcanoes.

      • Example: Andes Mountains.

  • Oceanic + Oceanic → subduction

    • One oceanic plate sinks beneath the other.

      • Forms volcanoes and deep ocean trenches.

  • Continental + Continental → collision

    • Neither plate easily sinks because both are relatively buoyant.

    • They crumple and push upward, forming mountains.

      • Example: Himalayas.

• Transform

  • Plates slide past each other 

  • The plates don't move smoothly all the time because friction causes them to get stuck. As the plates keep trying to move, stress builds up in the rocks.

  • Eventually, the rocks break/slip suddenly, releasing the stored energy as seismic waves → causes an earthquake.

    • Example: San Andreas Fault

Earthquakes

• Earthquake

  • Sudden release of stored energy when rocks break or slip along a fault.

• Fault

  • A fracture in Earth’s crust where rocks move.

• Focus (hypocenter)

  • The point inside Earth where the earthquake starts.

• Epicenter

  • The point on Earth’s surface directly above the focus.

Volcanoes and Magma

• Magma: Molten rock below Earth's surface.

• Lava: Magma that reaches Earth's surface.

• Volcano: An opening where magma, gases, and ash reach the surface.

• Types of Volcanoes

  • Shield Volcano

    • Broad, gently sloping sides.

    • Runny, low-viscosity basaltic lava.

      • Less explosive.

  • Composite Volcano (stratovolcano)

    • Tall, steep-sided cone.

    • Layers of lava, ash, and rock.

      • Viscous magma → more explosive.

  • Cinder Cone

    • Small, steep-sided volcano.

    • throw cinders/ash into the air

    • Usually forms around a single vent.
      
      

• Magma Types 

  • More silica → thicker/more viscous magma → more explosive

  • Less silica → runnier magma → less explosive