General Science Review: Stars, Solar System, and Cosmology - PDF

Bratovz 1 General Science Test #4 Review Why are stars important? -​ Navigation, Culture, Light & Energy -​ Elements: Nearly all elements formed during a star’s life cycle (except hydrogen, helium, and lithium). You are a star child What is a star? -​...

Bratovz 1 General Science Test #4 Review Why are stars important? -​ Navigation, Culture, Light & Energy -​ Elements: Nearly all elements formed during a star’s life cycle (except hydrogen, helium, and lithium). You are a star child What is a star? -​ Immense balls of hydrogen and helium with fusion occurring inside Astronomy -​ Studies celestial objects and phenomena using math, physics, and chemistry. -​ Objects include planets, moons, stars, nebulae, galaxies, and comets. Tools of the Trade -​ Electromagnetic radiation is the main source of information. -​ Types of telescopes: Optical & Radio. -​ Astronomers measure: -​ Wavelength -​ Intensity -​ Direction/position -​ Variations over time Galileo Galilei -​ Recorded telescope observations (1609). -​ Coined “telescope” from Greek tele (far) + skopos (seeing). -​ Used a refracting telescope.  Bratovz 2 Orbiting Observations -​ Earth’s atmosphere absorbs many space waves. -​ Satellites provide an unobstructed view. Future Telescopes -​ Use segmented mirrors for adjustments. -​ Most are being built in the Atacama Desert, Chile. The Sun: A Giver of Life & Knowledge -​ Studying the Sun helps us understand other stars. Surface of the Sun -​ We only see the thin outer photosphere (~150 km deep). -​ No sharp boundary, just gas and energy. -​ During a total eclipse, the chromosphere and corona become visible. Chromosphere and Corona -​ This halo of plasma is usually hidden by the Sun’s light. -​ The Sun constantly emits solar wind (ions of helium & hydrogen from fusion). -​ Aurora Borealis: Charged particles interact with Earth’s atmosphere (oxygen & nitrogen), creating dancing colors. Northern Lights -​ The Sun emits charged particles (plasma). -​ Earth's magnetic field protects against most particles. -​ Large solar emissions can overpower the magnetic field. -​ When particles enter the atmosphere, chemical reactions release photons, creating the lights. How Much Energy Does the Sun Have? -​ 19th-century scholars estimated 10,000 years if the Sun burned coal. Nuclear Fusion -​ The Sun is powered by nuclear fusion, not coal. -​ Hydrogen fusion creates helium and releases energy. -​ Hydrogen is the most common element in the universe.  Bratovz 3 Nuclear fusion in the sun (3 step process) How Much Energy Does the Sun Have? -​ Total lifetime: ~11 billion years. -​ Current age: ~5 billion years. -​ When hydrogen runs out, the Sun will become a red giant, not disappear.  Bratovz 4 Where Do Stars Come From? -​ Nebular Hypothesis: Most widely accepted model. Nebular Hypothesis -​ Nebula: Large cloud of dust and gas forms. -​ Common in our galaxy. -​ Gravity pulls particles together, causing the nebula to collapse and spin faster. What Keeps a Star Together? -​ Heat & pressure push outward, while gravity pulls inward. -​ A star’s size depends on its mass (gravity) and heat/pressure. Life Cycle of Stars The Cycle of Stars -​ A star's fate depends on its mass of hydrogen and helium. -​ Brown Dwarfs: Low-mass stars (~10% of the Sun’s mass) have weak gravity, slow fusion, are dim, but can glow for a hundred billion years.  Bratovz 5 Life Cycle of Massive Stars -​ Massive Stars (>10% of the Sun’s mass) end in supernova or black holes. -​ Most stars fuse hydrogen rather than helium—and stop there. -​ Largest stars fuse elements up to iron, forming an iron core that can’t fuse further. -​ Without fuel, gravity causes rapid collapse (within ¼ second). -​ Supernova: Shockwaves explode the star, radiating light for months before fading. -​ Black Holes: Formed from the most massive stars. -​ Extremely dense with gravitational pull strong enough to trap light. -​ Grow over time due to immense mass. Chapter 15: Cosmology Edwin Hubble -​ 1917: A 100-inch Hooker Telescope was built near LA, California. -​ 1919: Hubble began working at Mount Wilson Observatory. -​ Used the telescope to study pulsating stars in nebulae. -​ Discovered Andromeda was ~2 million light-years away, proving it was a galaxy, not part of the Milky Way. -​ This led to a new branch of astronomy. Key Terms -​ Astronomy: Study of celestial bodies & the universe. -​ Cosmology: Study of the origin & evolution of the universe. -​ Galaxy: System of stars, dust, gas, and dark matter bound by gravity. -​ Andromeda: A galaxy (not a nebula). -​ Nebula: A cloud of dust & gas in space. -​ Solar System: Term for our Sun & its planets, but there are 3,000+ other stars with planets in the Milky Way. Galaxies -​ Hubble showed the universe is bigger than the Milky Way. -​ Billions of galaxies, each with millions to hundreds of billions of stars. -​ The Milky Way is a spiral galaxy. Detecting Galaxies -​ Long-exposure photos of empty sky regions reveal galaxies. -​ 1 universe -​ 100+ billion galaxies -​ Billions of trillions of stars Red Shift -​ Hubble found that galaxies appear redder than expected, indicating movement.  Bratovz 6 Doppler Effect Hubble's Law -​ Things moving away experience red shift, and the faster they are moving away from us the redder they are -​ Hubble notices that celestial objects showed more red shift the further they were from us. This means that distant objects are moving away from us faster than nearby objects -​ Hubble's law: galaxies are moving away from earth at speeds proportional to their distance. In other words, the further away they are, the faster they are moving away from earth Big Bang Theory -​ The universe began at a specific time and has been expanding ever since. -​ Describes expansion from a high-density, high-temperature state. -​ Does NOT explain how energy, time, or space were created. -​ A theory is not just a guess—it must be tested and repeatedly supported. Evidence for the Big Bang Theory 1. Universal Expansion -​ Hubble’s discovery of the universe's expansion was the first strong evidence. -​ Suggests that everything was once together. -​ Not conclusive—other theories (e.g., steady-state universe) could explain expansion, but they lack strong support. 2. Cosmic Microwave Background (CMB) -​ Radio astronomers detected a constant microwave hiss from all directions. -​ Ruled out interference (even pigeon poop). -​ The steady-state theory does not predict this, but the Big Bang theory does.  Bratovz 7 3. Abundance of Light Elements -​ Big Bang models predict early formation of hydrogen, helium, and lithium. -​ Heavier elements formed later in stars via nuclear fusion. -​ Observed element ratios match Big Bang predictions. Quick Review -​ The Great Debate: Were nebulae nearby dust clouds or faraway galaxies? -​ Hubble proved they were galaxies beyond the Milky Way. -​ He discovered universal expansion and founded cosmology. -​ If the universe is expanding, it must have once been compact. -​ The Big Bang Theory best explains this expansion. Key Takeaways -​ The universe was once extremely small, then rapidly expanded (inflation). -​ All forces were once united, with gravity separating first. -​ Gravity remains crucial in shaping the universe, stars, and beyond The Future of Our Universe -​ The universe is expanding, but will it expand forever? -​ 3 models depend on gravity’s ability to slow or stop expansion. -​ The key question: Is there enough mass for gravity to stop expansion? The 3 Models of the Universe -​ Closed Universe (Sphere-shaped) -​ Like a rubber band pulling back together. -​ Gravity stops & reverses expansion → leads to a Big Crunch. -​ Open Universe (Saddle/Pringles chip shape) -​ Like a rubber band that snaps. -​ Gravity can’t stop expansion, so expansion goes on forever. -​ Flat Universe (Sheet of paper shape) -​ Like a rubber band that stretches but stops expanding. -​ Gravity slows expansion indefinitely but never reverses it Dark Energy -​ Objects farther from the center need more energy to stay in motion. -​ Distant objects should orbit slower if forces were equal—but they don’t. -​ This suggests an unknown force (dark energy) is accelerating expansion. Dark Matter -​ Mysterious matter that has mass but doesn’t interact with normal objects. -​ It’s invisible but exerts gravitational pull. -​ 5x more abundant than normal matter. -​ Theorized to weakly interact with normal matter.  Bratovz 8 Dark Matter vs. Dark Energy Dark Matter Dark Energy Doesn’t emit light, but has gravity Unknown energy accelerating expansion Might be tiny, abundant subatomic particles Makes up ~70% of the universe (WIMPs) Explains galaxy rotation & gravitational effects Discovered through supernova observation Chapter 16: The Solar System The Solar System -​ 8 planets (divided into two types) -​ Asteroid belt (between Mars & Jupiter) -​ Kuiper belt (beyond Neptune, rhymes with "viper") What is a Planet? According to the International Astronomical Union (IAU), a planet must: 1.​ Orbit a star (our Sun). 2.​ Be massive enough for gravity to form a spherical shape. 3.​ Clear its orbit of similarly sized objects. Why Isn’t Pluto a Planet? -​ Pluto is too small to clear its orbit. -​ Charon (Pluto’s largest moon) is nearly the same size and affects Pluto’s motion. -​ Pluto is classified as a Dwarf Planet. Not the first downgrade! -​ Ceres was considered a planet in 1801 but reclassified as an asteroid in the 1860s. Measuring Distance in Space: Astronomical Units (AU) -​ 1 AU = Earth-Sun distance (~150 million km). -​ Relative Distances in AU: -​ Mercury ~0.4 AU -​ Venus ~0.7 AU -​ Earth ~ 1 AU -​ Mars ~1.5 AU -​ Jupiter ~5 AU -​ Saturn ~10 AU -​ Uranus ~20 AU -​ Neptune ~30 AU -​ Pluto ~40 AU  Bratovz 9 Formation of the Solar System: Nebular Hypothesis -​ Interstellar gas & dust collapsed under gravity. -​ Most material formed the Sun (heating up until nuclear fusion began). -​ Leftover spinning material formed planets & other objects. Why Are the Planets Far From the Sun Much Larger? -​ These planets are less dense and consist mostly of lightweight materials like gases. -​ Without mass to generate enough gravity, these planets expand and balloon out, unlike the Terrestrial Planets that are tightly held together. Terrestrial Planets: Formation -​ The protoplanetary disc was made of dense mineral grains and solids orbiting the Sun. -​ Over time, grains collided and stuck together, forming planetesimals (boulders to small mountains). -​ These collided and formed protoplanets—and the process got chaotic from there! Giant Game of Cosmic Billiards -​ 20-30 protoplanets orbited the Sun. -​ Some were sucked into the Sun. -​ Some escaped the Sun’s pull and shot into space. -​ Many collided with each other. -​ Debris from these collisions, and other sources, scattered and slammed into protoplanets, generating immense heat.  Bratovz 10 Differentiation -​ The intense heat from collisions caused the forming planets (like Earth) to melt completely. -​ Gravity caused heavier materials (like iron and nickel) to sink to the core, forming the solid/liquid core. -​ Lighter materials floated, forming the mantle and crust. -​ This process, called differentiation, occurred in all 4 terrestrial planets. The Moon -​ Big Splash Theory: Around 4.5 billion years ago, a planet named Theia collided with Earth. The resulting debris formed the Moon. Why is the Moon Less Dense than Earth? -​ Earth had already undergone differentiation when the Moon formed. -​ Heavy materials had sunk to Earth’s core, while the Moon formed from the lighter mantle material. -​ Moon rocks confirm this, showing it's made mostly of lighter material compared to Earth’s core. The 4 Terrestrial Planets Mercury (Closest to the Sun) -​ Visible as a fast-moving star -​ 0.4 AU from the Sun -​ About 1/3 the size of Earth, but equally as dense -​ Massive iron-nickel core -​ After differentiation, a collision with a protoplanet may have ripped off its mantle -​ No atmosphere -​ Surface is covered with craters, as there's no weathering process to erase them -​ In 2018, European and Japanese space agencies launched Bepi-Colombo, set to reach Mercury in 2025 Venus (2nd Closest to the Sun) -​ 85% of Earth's mass -​ Most Earth-sized planet -​ Atmosphere is largely CO2, leading to a runaway greenhouse effect -​ With no plants or life to absorb CO2, the planet has heated to about 462°C Earth (3rd Closest to the Sun) -​ Earth’s conditions support life—ideal atmosphere, water, and temperature  Bratovz 11 Mars (4th Closest to the Sun) -​ 1/10th the mass of Earth -​ Very thin atmosphere, mostly CO2, equivalent to being 40 km above sea level -​ Most explored and studied planet (other than Earth) -​ In 1971, the first spacecraft orbited Mars and found channels, indicating liquid water once existed -​ In 1976, Viking 1 and 2 landed, analyzing samples with methane in the atmosphere, suggesting potential microbial life or non-living chemical reactions -​ 6 rovers have landed, including: -​ Curiosity (2012, still active) -​ Perseverance (2021, with a drone) -​ Mars has ice, and liquid water may exist below its surface -​ Jezero Crater, targeted by Perseverance, was an ancient river delta where water once flowed -​ Perseverance uses a drill to search for life below the surface, with 30 sample tubes to return to Earth in the 2030s Asteroid Belt -​ Located between the terrestrial and Jovian planets -​ Portrayed as a dense collection of asteroids, but actually incredibly sparse -​ Previously thought to be a broken-up planet, but now understood to be material that never formed a planet, likely due to the gravitational influence of Jupiter Jovian Planets (sometimes called gas giants, but Uranus and Neptune contain large amounts of "ices") -​ Composed mostly of hydrogen, helium, and ices (such as water, ammonia, methane) -​ These planets are much larger than terrestrial ones and have thick atmospheres -​ Jupiter, Saturn, Uranus, and Neptune make up the Jovian planets Jupiter -​ Largest planet in the solar system -​ Mass is 317x that of Earth, and twice the mass of all other planets combined -​ Has a rocky core surrounded by metallic hydrogen (produced by immense pressure) -​ Most of Jupiter is solid or liquid metal -​ Rings made mostly of dust, hard to see but 30-12,000 km thick -​ Layers of Jupiter:  Bratovz 12 -​ Liquid hydrogen -​ Gaseous hydrogen -​ Cloud tops -​ The planet's distinct coloured bands and the Great Red Spot (a storm larger than Earth that has raged for hundreds of years) -​ The bands are similar to Earth's trade winds, but Jupiter’s faster rotation (once every 10 hours) makes them bigger and stronger Europa (Jupiter’s Moon) -​ Jupiter has 61 moons, with Europa being the size of Earth's moon -​ In 1995, the Galileo spacecraft detected that beneath Europa's frozen outer surface, there is likely more water than on Earth -​ Gravitational pull from Jupiter keeps the water liquid, and recent measurements indicate saltwater oceans -​ Hypothesis suggests that Europa could harbor the building blocks of microbial life -​ Galileo spacecraft was deliberately crashed into Jupiter to avoid contamination of Europa -​ Human colonization of Europa is a possibility for the distant future Saturn -​ Jupiter and Uranus have rings, but none compare to Saturn's rings -​ Less dense than Jupiter, and less dense than liquid water, making it the least dense planet -​ Rings are viewed only from above -​ The average thickness of Saturn's rings is 10 meters -​ Rings are made of countless small pieces of rock and ice -​ The rings may have resulted from a moon that was broken apart by Saturn's gravity Titan (Saturn’s Moon) -​ Largest moon in the solar system -​ The only moon with an atmosphere -​ The Cassini spacecraft orbited Titan from 2004-2017 -​ Titan features oceans of liquid methane and mountains of water ice Enceladus (Saturn’s Moon) -​ Another of Saturn's moons -​ The Cassini spacecraft detected a subsurface ocean and more than 100 geysers of liquid water erupting from the surface -​ Cassini flew through these geysers and found molecules similar to those produced at mid-ocean vents on Earth (where life may have begun) -​ As a result, Cassini was crashed into Saturn to avoid contaminating Enceladus  Bratovz 13 Uranus -​ An ice giant and the 2nd least dense planet -​ Has 21 moons -​ Appears bluish due to methane in the atmosphere, which absorbs red wavelengths -​ Has rings, but made of sparse and dark material -​ Uranus is the only planet that rotates as if it were “lying down”—likely caused by a collision early in its history Uranus Summarized -​ Uranus is cold, gassy, and not dense -​ The planet is "lying down" (due to an early collision) -​ It has rings and moons Neptune -​ An ice giant, gassy planet -​ 4x wider than Earth -​ A 16-hour day, but it takes 165 Earth years to orbit the Sun -​ 14 moons -​ Rings confirmed by Voyager 2 in 1989, the only spacecraft to visit Neptune -​ Rings are composed of dust and ice Chapter 17: Plate Tectonics What is an Earthquake? -​ A sudden, violent shaking of the ground caused by movements within the Earth's crust. -​ Seismic waves are generated by the release of energy in the Earth's lithosphere, causing shaking at the surface. -​ Earthquakes (and volcanoes) are signs of the Earth's inner forces. -​ Earth has many layers, typically discussed as three to five: -​ Core, mantle, crust -​ Inner core, outer core, mantle, crust -​ Inner core, outer core, mantle, upper mantle, crust Can We Predict Earthquakes? -​ Earliest references to animals predicting earthquakes date back to 373 BC in Greece, with animals like rats, weasels, snakes, and centipedes fleeing their homes before a major quake. -​ US Geological Survey reports there's a 100% chance of an earthquake happening somewhere today. -​ Predictions must define three elements: time, location, and magnitude. -​ No reliable predictor for dangerous earthquakes exists. -​ To understand earthquakes, it's essential to study plate tectonics, which stemmed from biologists exploring life distribution on Earth.  Bratovz 14 Biogeography -​ The study of how species and ecosystems are distributed geographically and through geological time. -​ Biogeography began as a way to understand why species are distributed as they are. Key Figures in Biogeography -​ Carolus Linnaeus (1707-1778): Swedish naturalist who sparked the field of biogeography. He formalized binomial nomenclature but believed species were fixed and unchanged, which later prompted questions about evolution. -​ Linnaeus and Noah's Ark: He reconciled species distribution with the Bible by suggesting species spread from the ark after it landed on a mountain. -​ Georges Buffon (1707-1788): French naturalist who proposed the "northern origin" hypothesis and recognized the dynamic nature of Earth and species. -​ Charles Darwin: Started with a literal belief in the Bible but, through his research, proposed that species evolve over time. Key ideas included: -​ Individuals vary in a population. -​ Variation is inherited. -​ Many offspring die before reproducing. -​ HMS Beagle: Darwin's research voyage from 1831-1836 that lasted 6 years. -​ Alfred Wallace: A naturalist who, alongside Darwin, co-founded the theory of evolution by natural selection and is considered the father of biogeography. Remaining Problem: Disjunctions -​ Disjunctions refer to cases where closely related species are found in distant places, which was a challenge for early biogeographers. -​ Darwin and others suggested dispersal was the primary mechanism for these disjunctions. Alfred Wegener (1880-1930) -​ Proposed the idea that continents were once connected and have since moved. His hypothesis was based on biological and geological evidence but lacked a way to test it. He died before it was validated. Plate Tectonics: From Hypothesis to Theory -​ Hypothesis: A tentative explanation based on observations that can be scientifically tested. It is an educated guess by experts. -​ Theory: A well-tested, widely accepted explanation for a phenomenon, backed by a broad range of data. A theory is the most robust scientific explanation before becoming a law, which is rare. Theory of Plate Tectonics -​ Plate tectonics explains how the Earth's crust (and upper mantle) is broken into a few, thin, rigid plates that move across the surface due to mantle convection. Convection involves the flow of fluid or gas caused by thermal differences (think: hot air rises). -​ These plates are "dragged" by the moving mantle, like rafts on the ocean.  Bratovz 15 Evidence Supporting Plate Tectonics 1.​ Geological Features of Ocean Floors: -​ Advances in sonar during WWII revealed the true structure of ocean floors. -​ Instead of flat plains, ocean floors have canyons, mountains, and ridges, with the longest being the Mid-Atlantic Ridge. -​ These discoveries supported the idea of seafloor spreading and helped explain the similar fossils found across continents like Africa and South America. 2.​ Magnetic Reversals: -​ Earth's magnetic field flips periodically. As lava cools, magnetic minerals align with Earth's magnetic field. These flips occur roughly every 1 million years. -​ The striped pattern of magnetic rocks on the ocean floor is mirrored on opposite sides of ocean ridges. This supported the theory of seafloor spreading. 3.​ Rock Ages: -​ Seafloor spreading: New molten rock emerges at ocean ridges, pushing existing rock outward. The polarity of rocks alternates as the Earth's magnetic field switches, creating a pattern that matches on opposite sides of ridges. Plate Tectonics: A Unifying View of Earth -​ The Atlantic Ocean formed via seafloor spreading at the Mid-Atlantic Ridge. It's 7,000 km wide, spreading at 5 cm/year. -​ Around 140 million years ago, there was no Atlantic Ocean, and the Americas were connected to Europe and Africa. This supports the theory of a single supercontinent, Pangea, which began breaking apart around 200 million years ago. Mantle Convection Causes Movement -​ Plate boundaries are where plates meet. There are three types of plate boundaries: -​ Divergent plate boundaries: Plates move away from each other, causing seafloor spreading where magma emerges and forms new rock. -​ Convergent plate boundaries: Plates move towards each other, often resulting in subduction or mountain formation. -​ Transform plate boundaries: Plates slide past each other, causing earthquakes. Divergent Plate Boundaries -​ Plates move away from each other, and new rock forms where magma rises from the mantle. -​ On the ocean floor, this forms basalt. On land, divergent boundaries can create rift valleys or split continents, leading to the formation of new oceans. -​ Mid-Atlantic Ridge is an example of a divergent boundary that stretches across the ocean floor  Bratovz 16 Convergent Plate Boundaries -​ Plates move towards each other, and the outcome depends on whether the plates are oceanic or continental. -​ Oceanic plates are about 10 km thick and made of dense basalt, while continental plates are about 35 km thick and made of lighter granite. Types of Convergent Boundaries: 1.​ Continent-Ocean Convergence: -​ The oceanic plate is denser than the continental plate, so it subducts (dives) below the continental plate. -​ This causes the formation of an offshore trench and volcanic mountains on the continent. -​ Example regions: Andes Mountains (South America), Cascades (Northwest USA). -​ As the oceanic plate is subducted, the pressure builds and erupts as volcanoes on the continental side. 2.​ Ocean-Ocean Convergence: -​ Both plates are oceanic, but one plate is slightly denser than the other. -​ The denser plate subducts beneath the lighter one, creating a deep ocean trench. -​ This type of boundary often forms volcanic island arcs in the ocean. 3.​ Continent-Continent Convergence: -​ Continental plates are less dense than oceanic plates (granite vs. basalt). -​ Instead of subduction, the plates collide, causing the crust to buckle and fold, creating large mountain ranges (no subduction, no volcanic activity). -​ Example: The Himalayas, where the Indian Plate and Eurasian Plate collide, forming some of the tallest mountains in the world. Volcanoes -​ Volcanoes can form in three main areas: 1.​ Divergent plate boundaries (where plates move apart). 2.​ Convergent plate boundaries (where plates collide). 3.​ Hotspots (in the middle of plates, not at plate boundaries). Hotspot Island Formation: -​ Hotspots are areas in the mantle where thin spots allow magma to rise as mantle plumes. -​ These plumes are relatively stationary, while the tectonic plate moves over them. -​ As the plate moves, volcanic islands are created in a chain. -​ The islands are sequentially arranged from oldest to youngest, with the oldest island farthest from the hotspot. -​ Example: Hawaiian Islands, where each island gets progressively younger as you move along the chain, and the direction of plate movement shifted around 43 million years ago.  Bratovz 17 Transform Plate Boundaries -​ Plates move past each other horizontally (not towards or away). -​ The most famous example is the San Andreas Fault in California, where the Pacific and North American plates slide past each other. -​ Friction keeps the plates from moving smoothly, causing stress to build until the rocks break along fault lines. -​ Unlike divergent or convergent boundaries, transform boundaries do not create mountains or volcanoes. -​ The massive energy released when the plates slip causes earthquakes along the fault lines. -​ The larger the section of the fault line involved, the greater the energy released during an earthquake. Rock Cycle The rock cycle is the continuous process by which rocks are created, destroyed, and altered in various ways over time. There are three primary types of rocks involved in the cycle: 1.​ Igneous 2.​ Sedimentary 3.​ Metamorphic Any type of rock can transform into another, depending on various geological processes like weathering, heat, pressure, or melting. -​ Sedimentary rocks can form from weathered and lithified (compacted and cemented) sediments. -​ Igneous rocks can form when any rock is melted down into magma and then solidifies. -​ Metamorphic rocks can form when any rock is subjected to extreme heat and pressure. Igneous Rocks -​ Igneous rocks were the first solids to form on Earth's ancient surface and are created from the cooling and solidification of molten materials (magma or lava). -​ Extrusive (or volcanic) igneous rocks form when magma cools and solidifies on the surface (e.g., basalt, pumice). -​ Intrusive igneous rocks form when magma cools and solidifies underground (e.g., granite). These may later become exposed at Earth's surface due to tectonic activity or erosion.  Bratovz 18 Three things can happen to igneous rocks: 1.​ Melting – Igneous rocks can melt down into magma and form new igneous rocks. 2.​ Metamorphism – They can be transformed into metamorphic rocks due to heat and pressure. 3.​ Weathering – They can be weathered (broken down into smaller particles) and form sedimentary rocks. Sedimentary Rocks -​ Sedimentary rocks form through the accumulation of particles at Earth's surface, followed by cementation (binding of particles together). -​ The source material for sedimentary rocks can be minerals from any type of rock or organic material. -​ For example, limestone is a common sedimentary rock formed from the accumulation of calcite and aragonite, which mainly come from marine invertebrates (such as corals and shelled organisms). -​ Sedimentary rocks often contain fossils of these organisms, which help geologists understand past environments. Sedimentary rocks generally form in layers, with older layers at the bottom, and can be found in a variety of environments, from riverbeds to ocean floors. Metamorphic Rocks Metamorphic rocks form when sedimentary or igneous rocks are exposed to intense heat and pressure deep within the Earth's crust. These conditions cause the minerals in the rocks to recrystallize or undergo chemical changes, resulting in new textures and structures. -​ Metamorphism refers to the process where existing rocks (either sedimentary or igneous) are transformed into metamorphic rocks under heat and pressure, without the rock melting. -​ The temperature and pressure conditions, as well as the presence of fluids, dictate the type of metamorphic rock formed.  Bratovz 19 Limestone to Marble -​ Limestone is a sedimentary rock that forms mainly from shell fragments and other fine particles, like sand or clay, that are cemented together. It's typically made of calcite or aragonite (both forms of calcium carbonate). -​ Under heat and pressure, limestone can metamorphose into marble, a metamorphic rock. -​ The heat and pressure cause the calcite in the limestone to recrystallize, which results in a more dense, crystalline texture. Marble is often prized for its aesthetic quality and is used in sculpture and architecture. Metamorphic Processes -​ Foliation: In some metamorphic rocks, pressure causes minerals to align in parallel layers, which can create a foliated texture (e.g., schist, slate). -​ Non-foliated metamorphic rocks (like marble or quartzite) do not show a layered structure, as the minerals crystallize in a more uniform pattern. Recycling into Magma -​ Metamorphic rocks, like other types of rocks, can eventually be recycled back into magma in a subduction zone, where one tectonic plate is forced beneath another. This process can cause the metamorphic rock to melt, forming new magma that may later cool and solidify into igneous rocks.