SCIENCE FIRST QT.

ORIGIN OF THE SOLAR SYSTEM

●​ NEBULAR THEORY
○​ idea that the solar system formed from a nebula (a large cloud of dust and
gas)
1.​ Interstellar gas cloud - is a large cloud of gas (mostly hydrogen) and dust floating in
space between stars.
2.​ Collapse due to gravity - Gravity pulls everything inward — gas and dust get closer
together.
3.​ Formation of protostar - As the collapsing cloud continues to shrink, its central
region becomes increasingly dense and hot, forming a protostar
4.​ Disk flattening - the collapsing cloud flattens into a rotating disk of gas and dust
around the protostar.
5.​ Planetesimal formation - Within the protoplanetary disk, dust grains collide and
stick together, gradually growing into larger solid bodies called planetesimals.
6.​ Clearing of Debris - This process leaves behind a more defined planetary system
with much less free-floating material.

●​ 3 MAIN HYPOTHESIS
○​ Nebular Hypothesis
This widely accepted theory posits that the Solar System formed from the
gravitational collapse of a rotating cloud of gas and dust, with the Sun forming
at the center and planets accreting from the surrounding disk.
○​ Encounter Hypothesis
This largely discredited theory suggested that planets formed from material
ripped from the Sun or another star during a close stellar flyby.
○​ Protoplanet Theory
This theory, a refinement of the nebular hypothesis, describes how
kilometer-sized planetesimals within the protoplanetary disk collide and
accrete to form larger protoplanets, which then become full-sized planets.

EARTH STRUCTURES AND SUBSYSTEMS

●​ Atmosphere
○​ Exosphere - Outermost layer merging w/ space
○​ Thermosphere - Auroras occur and satellites appear here
○​ Troposphere - Meteors burn up here
○​ Stratosphere - Ozone layer
○​ Mesosphere - Closest to Earth, where weather occurs
●​ Hydrosphere
○​ Includes all water on Earth (oceans, lakes, rivers, glaciers, groundwater).
○​ Covers about 71% of Earth’s surface.
○​ Essential for climate regulation and life
●​ The Lithosphere
○​ Rigid outer shell of Earth (includes crust and uppermost mantle).
○​ Broken into tectonic plates that move slowly.
○​ Interacts with the asthenosphere (semi-fluid layer beneath it).
○​ Supports landforms (mountains, continents, ocean floors).
●​ Earth’s Internal Structure
○​ Crust - Solid outer layer (continental & oceanic).
○​ Asthenosphere - Semi-fluid part of the upper mantle; plates slide on it.
○​ Mantle - Thick, semi-solid rock layer (upper and lower mantle).
○​ Outer Core - Liquid iron/nickel; generates magnetic field.
○​ Inner Core - Solid iron/nickel; hotter than the Sun’s surface
●​ Fun Facts
○​ The troposphere is where airplanes fly.
○​ The lithosphere is about 100 km thick.
○​ Earth’s crust is thinner than an eggshell relative to Earth’s size!
○​ Without the outer core, Earth would have no magnetic shield.

●​ Continental Drift Theory

○​ Proposed by German meteorologist and geophysicist Alfred Wegener in 1912
○​ Pangea (all-earth) - Earth’s continents were once joined into this super earth
○​ over time, the continents broke apart, making smaller continents drift to their
current positions
○​ Africa’s western coast + SA’s eastern coast fit together like a jigsaw puzzle
■​ Fossil Evidence - Identical fossilized remains of ancient plants and
animals have been found on continents that are now widely separated
by vast oceans.
●​ Mesosaurus: A freshwater reptile whose fossils are found only
in South America and Africa.
●​ Glossopteris: A distinctive fern whose fossils are found
across South America, Africa, Australia, India, and Antarctica.
■​ Matching Rock Types - Similar rock formations, geological
structures, and mountain ranges are found on different continents,
suggesting they were once part of a continuous geological feature that
was later separated.
ORIGIN THEORIES
●​ The Big Bang Theory (Georges Lemaitre proposed, Edwin Hubble supported)
○​ This theory suggests that about 13.8 billion years ago, the entire observable
universe was condensed into an incredibly hot, dense point – smaller than an
atom! Then, it began to rapidly expand, cool, and eventually, matter formed,
leading to stars, galaxies, and everything we see today.
○​ It wasn't an explosion in space, but rather an explosion of space itself. There
was no "outside" for it to explode into!
○​ CMB radiation is key evidence. universe still expanding today
●​ Steady State Theory (Fred Hoyle, Thomas Gold, Hermann Bondi)
○​ no beginning, no end. matter is continuously created. no bounds in space or
time, universe looks the same everywhere
○​ This theory proposes that the universe has always existed and will always
exist in pretty much the same state. It's constantly expanding, but new matter
is continuously created spontaneously to fill the space left by expanding
galaxies. This keeps the overall density of the universe constant.
○​ Why it's less accepted now: The discovery of the Cosmic Microwave
Background (CMB) and the observation that galaxies were different in the
past (e.g., more quasars) strongly contradicted this theory. The CMB showed
a hot, dense past, not a "steady state."
●​ Oscillating Universe (Richard Tolman proposed, Paul Steinhardt and Neil Turok
developed)
○​ universe undergoes cycles of expansion and contraction, each potentially
creating new universes or dimensions
○​ The Oscillating Universe theory suggests that our universe is just one in an
endless series of "Big Bangs" and "Big Crunches." It proposes that the
universe expands to a certain point, then gravity eventually pulls all matter
back together into a super-dense state (a "Big Crunch"), from which another
Big Bang then emerges.
○​ Current observations suggest that the universe's expansion is actually
accelerating, driven by something called "dark energy." This accelerated
expansion makes a future "Big Crunch" seem unlikely based on current data,
casting doubt on a simple oscillating model.
●​ Cosmic Microwave Background radiation -
CLASSIFYING ROCKS
●​ Igneous
○​ lava/magma crystallizing
○​ cooling/solidification
○​ Types
■​ Intrusive - when magma slowly cools, resulting in large crystals
(granite)
■​ Extrusive - when lava cools quickly (obsidian), leaving small crystals
and glassy texture
●​ Sedimentary
○​ accumulation & cementation of sediments
○​ often have fossils + clues about the past environment
○​ Types
■​ Clastic - compacted broken rocks (sandstone)
■​ Chemical - compacted dissolved materials (limestone)
■​ Organic - compacted biogenic matter (coal)
○​ ex.: shale, siltstone, conglomerate
●​ Metamorphic
○​ layered/banded appearance
○​ from pressure, heat, chemical processes
○​ from existing rocks that morph underground
○​ Types
■​ Foliated (slate) - have layered appearance bc of alignment of
minerals under directed pressure (one direction)
■​ Non-Foliated (marble) - no layered appearance bc of pressure
applied from all directions equally/original rock’s composition doesn’t
allow layering

MINERAL PROPERTIES
●​ Minerals
○​ naturally occurring, inorganic solids w/ specific chemical compositions
○​ over 5k mineral species exist on Earth
○​ unique physical properties
​ PHYSICAL PROPERTIES
1.​ Luster
●​ how shiny/how light reflects on mineral’s surface
 ●​ first thing noted when examining a specimen
●​ Types
○​ Metallic - shiny like polished metal/mirror
○​ Non-metallic - vitreous (glass-like), pearly, dull (clay, talc, etc.)
2.​ Color
●​ not reliable–depends on environments, etc.
●​ apparent hue, not good for identifying
●​ impurities alter appearance
●​ some minerals maintain consistent color: malachite (bright green), azurite
(deep blue)
3.​ Streak
●​ true color
●​ color when mineral powder is rubbed on unglazed porcelain plate
●​ more reliable bc it removes weathering effect
●​ ex.: hematite - silver/black outside, truly reddish-brown
4.​ Hardness
●​ resistance to scratching
●​ Mohs scale (1-10); soft-hard

talc 1 fingernail 2.5

gypsum 2 copper penny 3.5

calcite 3 glass 5.5

fluorite 4 mineral x > 5.5

scratches glass
apatite 5

feldspar 6

quarts 7

topaz 8

corundum 9

diamond 10

5.​ Cleavage & Fracture

●​ Cleavage - tendency of mineral to break alone specific planes of weakness
●​ Fracture - way a mineral breaks with no weak planes/doesn’t cleave
 6.​ Specific Gravity
●​ compares mineral’s density to water (1.0)
●​ heft test, how heavy something feels relative to its size

WEATHERING
●​ process of breaking down rocks, soils, minerals right where they are
●​ Earth’s constant sculptor, creates landforms
●​ unlike erosion, weathering acts in place without moving material
●​ causes: wind, water, temperature, ice, plants, animals

​ TYPES
●​ Mechanical - physically breaks rock into smaller pieces without changing
composition
○​ frost wedging - water freezes in cracks, expands by 9%, prying rocks apart
○​ abrasion - grinding/wearing away of rock by friction and impact
○​ exfoliation - layers are gone, overlying pressure is removed causing rock to
expand and peel in layers
○​ block integration - extreme temperature changes cause rocks to expand
and contract, leading to features
●​ Chemical (key agents: water/oxygen, co2, acids) - weakening/disintegration of rocks
and formation of new compounds/substances by chemical reactions and too much
exposure to an environment. shapes landscapes, form soils, release minerals from
rocks
○​ oxidation - where oxygen reacts with rock that has iron-like parts, turns it into
rust
○​ carbonation - soluble materials carried by water with minerals like calcium
carbonate (limestone), reaction w CO2. formation of types of carbonates in
rocks, where some carbonates are soluble
○​ hydration - absorption/combination of water + substance on rock, leading to
change in shape (expand and weaken-bubble)
○​ solution/dissolution - where some minerals in rock are direct dissolved in
water rock is weekend, deformed, pieced, disintegrated
●​ Biological
○​ root wedging - tree roots grow into cracks, exerts immense pressure as they
enlarge, forcing rocks apart
○​ animal burrowing - prairie dogs/rabbits dig into soft rock/soil. expose new
surfaces to other weathering agents
 ○​ organic acid production - unwanted growing moss/they secrete acid that
dissolve rock minerals, creating greenish/grayish film on surfaces
○​ humans - provisions for agriculture + construction need broken down rocks

EROSION
●​ mass wasting - downslope movement of rock, soil, debris under gravity’s influence
○​ from: water saturating ground, reducing friction; seismic activity destabilising
slopes; steep slopes
●​ rapid mass wasting events
○​ rockfall - free falling rock pieces from cliffs/steep slopes. common in
mountainous areas w/ exposed rock faces
○​ debris flows - fast moving liquid mix of water, soil, rock w/ wet cement
consistency. highly destructive to infrastructure
○​ landslide - rapid movement of rock + earth masses
■​ translational - movement along planar surface
■​ rotational (slumps) - movement along curved slip surface
SOIL EROSION - detachment + transport of topsoil by natural agents and human activities
●​ natural erosion - geological process occurring over millenia
​ TYPES
●​ sheet erosion - removal of thin layers bc or surface runoff + rain
●​ rill erosion - removal of soil by action of concentrated running water
●​ gully erosion - removal of soil in water channels/drainage lines
EROSION
●​ in which weathered rocks and soil are transported elsewhere
●​ cause: water (river, etc); wind (strong gusts); ice (glaciers pick up, dragging large
rock and debris); gravity (direct downhill movement of material - landslide, etc)
DEPOSITION
●​ dropping/settling of sediments in new location
○​ loss of energy - when natural agents can’t move rocks any more
○​ sediment settling - heavier, larger sediments deposit first; then finer
materials
○​ landform creation - accumulation of sediments. creates landforms (sand
dunes, deltas, alluvial fans)
VOLCANOUS, MAGMA, PLATE TECTONICS
●​ volcanoes - openings in Earth’s crust where molten rock escapes, creating dramatic
landscapes
○​ approx. 1,900 active volcanoes worldwide
○​ magma: beneath surface; lava: when erupted
○​ eruptions release gas, ash, pyroclastic materials
○​ shapes landscapes through destruction + creation
●​ formation - magma forms when mantle/crustal rock melts under intense pressure +
heat conditions within Earth’s interior (radioactive decay to internal heat)
●​ viscosity - low-viscosity basaltic magma flows easily, creating shield volcanoes
(Mauna Loa - Hawaii)
●​ explosivity - high-viscosity, gas-rich magma cause violent eruptions, building
stratovolcanoes (Mt. Fuji)
●​ movement - magma rises through cracks + fissures driven by buoyancy and
expanding gases trapped within

PLATE TECTONICS
●​ lithosphere is fragmented into massive sections that float on semi-fluid
asthenosphere beneath
​ ALFRED WEGENER
●​ geophysicist
●​ proposed Continental Drift Theory
○​ continents were once joined into Pangea
○​ drifted bc of plate tectonic movement
●​ 7 major plates - Pacific, North American, South American, Eurasian, African,
Antarctic, Indo-Australian\
●​ minor plates - Nazca, Cocos, Caribbean, Arabian, Indian, Novia Scotia, Somail,
Juan de Fuca, Philippine

PLATE BOUNDARIES + MOVEMENT - where plate/s end/s

​ TYPES
●​ Divergent (nag-buwag)
○​ 2 plates move apart
○​ gap filled w/ rising magma from asthenosphere
○​ allows magma to form new crust
●​ Convergent (nag-balik)
○​ move towards eo/collide
 ○​ different edges: 2 oceanic, 2 continental, 1 oceanic and 1 continental
●​ Transform (move parallel to eo)
○​ slide past eo horizontally
○​ in oceanic crust/continental crust (San Andreas fault in Cali)
DEFORM: folding + faulting
●​ orogenesis - creation of mountain (earth/rocks/mountain +
beginning/formation)
●​ folding - stress due to compression of tectonic plates, gradual process. rock layers
fold in direction of plunge
○​ 2 sections - anticline (upward fold); syncline (downward fold)
●​ plunging - towards eo/converging. combination of continental and divergent plate
●​ fault - fracture in crust where significant displacement has occurred. crack/fracture
where sides are relative to eo
○​ normal - hanging wall goes down
○​ reverse - hanging wall goes up
○​ strike-slip - sideways

●​ footwall - stays dormant