Learn: 5005 Earth science

Continental Crust

Thicker layer of the Earth's crust forming continents.

Oceanic Crust

Thinner layer of the crust located beneath oceans.

Crust Thickness

Typically 30 to 60 km thick.

Upper Mantle

Top section of the mantle, roughly 700 km deep.

Lower Mantle

Deeper section of the mantle under higher pressure.

Lithosphere

Rigid, solid combination of the crust and the solid uppermost mantle.

Asthenosphere

Deeper, plastic/deformable mantle layer functioning like high-viscosity magma.

Core Composition

Predominantly nickel and iron; heavy elements sank to the center during formation.

Outer Core

Liquid layer, approx. 2,300 km thick; low viscosity allows fluid flow.

Inner Core

Solid layer, approx. 1,200 km thick; extreme pressure prevents molecules from flowing despite high heat.

Chemical vs. Mechanical Layers

Distinctions like crust/mantle are based on chemistry, while lithosphere/asthenosphere are based on mechanics.

Pressure Rule

As you dig deeper, gravity increases downward pressure, turning potential liquids into solids.

Mantle Size

Largest layer by volume; composed of different rock types than the crust.

Mesosphere

Lower mantle; high pressure makes this layer rigid and solid.

LAMO Mnemonic

Stands for Lithosphere, Asthenosphere, Mesosphere, Outer Core from surface to center.

P-waves

Compressional waves that travel through all states of matter: solid, liquid, and gas.

S-waves

Transverse waves that can only travel through solids.

S-wave Shadow Zone

Absence of S-waves beyond 105 degrees indicates they encounter a liquid layer.

P-wave Refraction

P-waves slow down and bend when entering the liquid outer core.

Continental Fit

The shape of continents, specifically South America and Africa, suggests they were once joined.

Mid-Ocean Ridges

Large underwater mountain ranges that are sites of volcanic activity and new crust formation.

Paleomagnetism

Molten lava contains minerals that align with Earth's magnetic poles as the rock cools.

Magnetic Striping

Alternating stripes of magnetic polarity on the ocean floor proving seafloor spreading.

Current Plate Speed

Most plates move at roughly one centimeter per year, comparable to human fingernail growth.

Hotspot Formation

Caused by localized, extremely hot magma rising from the mantle due to lower density.

Rifting Phase

Magma pushes upward, thinning the crust and creating depressions known as Rift Valleys.

Submersion Phase

Land sinks below sea level as rifting continues, allowing water to flow into the basin.

African Rift Valley

An early-stage example of a land-based rift valley created by a hotspot.

Red Sea

A mid-stage rift example deepened enough to be filled by seawater.

Mid-Atlantic Ridge

A mature divergent boundary with a vast ocean floor and continuous volcanic mountain chain.

Convergent Boundary

A region where tectonic plates move toward and collide with one another.

Subduction

The process where one plate is pushed underneath another due to density differences.

Trench

A deep, elongated depression in the ocean floor formed during subduction.

Oceanic-Continental Collision

Denser oceanic crust subducts under continental crust, creating trenches and volcanic mountain ranges like the Andes.

Oceanic-Oceanic Collision

Older, denser oceanic plate subducts, forming deep trenches like the Mariana Trench and island arcs.

Continental-Continental Collision

Neither continental plate subducts easily, forcing crust upward into massive mountain ranges like the Himalayas.

Convection

Heat transfer in fluids where warmer, less dense material rises and cooler, denser material sinks.

Drag Force

Viscous movement of the mantle that pulls overlying lithospheric plates along.

Ridge Push and Slab Pull

Gravitational effects where cooling, thickening plates sink further away from ridges.

Surface Seismic Waves

Seismic waves that travel across the Earth's surface like ripples on water.

Rayleigh Waves

Surface waves where the ground moves up and down.

Love Waves

Surface waves where the ground shifts side to side.

Body Waves

Seismic waves traveling through the interior of the Earth; faster than surface waves.

Biogeochemical Cycles

Cycles involving essential molecules circulating through an ecosystem and the biosphere.

Essential Elements for Life

Water, Carbon, Nitrogen, and Phosphorus.

Energy Flow vs Matter

Energy flows from the sun and dissipates as heat, whereas matter is constantly recycled.

Evaporation

Liquid water gains energy and turns into gaseous water vapor.

Condensation

Water vapor cools and turns back into liquid droplets to form clouds.

Precipitation

Condensed water droplets grow heavy and fall as rain, snow, or ice.

Sublimation

Direct phase change from solid ice to gaseous water vapor.

Transpiration

Evaporation of water specifically from the leaves of plants.

Percolation

Water moving downward through soil into the ground.

Runoff

Water traveling over the surface into creeks, rivers, and lakes when ground is saturated.

Earth Water Distribution

97.5 percent salt water in oceans; 2.5 percent fresh water.

Fresh Water Breakdown

The vast majority of fresh water is held in glaciers and permanent snow.

Supernova Trigger

A local supernova shockwave compressed a gas cloud, initiating gravitational accretion.

Sun Ignition

Compressed gas reached critical temperature and pressure, triggering hydrogen-to-helium nuclear fusion.

Accretion

Particles and gas orbiting the young Sun collided and clumped due to gravity.

Theia Impact

A Mars-sized protoplanet struck Earth, making both molten and ejecting material that formed the Moon.

Hadean Eon

Earliest geological eon (4.6 to 4 billion years ago) characterized by a molten, inhospitable surface.

Late Heavy Bombardment

Period of intense asteroid collisions caused by gravitational shifts of Uranus and Neptune.

Prokaryotes

Single-celled organisms lacking a nucleus and membrane-bound organelles, such as bacteria and archaea.

Eukaryotes

Organisms possessing a nucleus enclosed in a membrane and specialized organelles like mitochondria.

Cyanobacteria

Photosynthetic bacteria that evolved around 3.5 billion years ago, oxygenating the oceans and atmosphere.

Hot Spot

A stationary area of intense heat located beneath a lithospheric plate, fueled by mantle plumes.

Hawaiian Age Gradient

Islands closest to the hot spot are youngest, while those further northwest are progressively older and eroded.

Pangaea

An ancient supercontinent that existed approximately 200 to 300 million years ago.

Fossils

The preserved remains or traces of organisms once alive, buried within rock layers over time.

Speciation

Evolutionary process documenting a single species splitting into two separate lineages.

Transitional Forms

Fossil organisms representing intermediate stages between different groups of species.

Moon Diameter

Roughly 2,200 miles, about one-fourth the size of Earth.

The 108 Ratio

Ratio of distance to diameter for both the Sun and Moon is approximately 108, making them look equal in size.

New Moon Phase

Moon is between Earth and Sun; the lit side faces away.

Full Moon Phase

Earth is between Moon and Sun; the entire lit side is visible from Earth.

Orbital Inclination of Moon

The Moon's orbit is tilted at a 5-degree angle relative to the ecliptic plane, making eclipses rare.

Umbra

The darkest, inner part of a shadow where the light source is completely blocked.

Penumbra

The outer, lighter part of a shadow where the light source is only partially blocked.

Astronomical Unit (AU)

The average distance from the Earth to the Sun, approximately 150 million kilometers.

Light-Year

A unit of astronomical distance equivalent to the distance light travels in one year.

Kuiper Belt

A region beyond Neptune's orbit containing icy bodies and frozen gases.

Oort Cloud

A hypothesized spherical shell surrounding the solar system, origin point for many comets.

Heliopause

The region where solar wind pressure is counteracted by the interstellar medium.

Alpha Centauri

The nearest star system to our own, approximately 4.2 light-years from Earth.

Milky Way Dimensions

A spiral galaxy approximately 100,000 light-years in diameter and 1,000 light-years thick.

Singularity

An infinitely small point from which the universe expanded in the Big Bang theory.

Perihelion

The point in Earth's orbit closest to the Sun, occurring in January.

Aphelion

The point in Earth's orbit farthest from the Sun, occurring in July.

Earth's Axial Tilt

Currently tilted at approximately 23.4 degrees relative to its orbital plane perpendicular.

Summer Solstice Factors

Hemisphere tilted toward the sun experiences more daylight hours, less darkness, and higher sun angles.

Scientific Hypothesis

A proposed, testable explanation for an observation.

Control Group

Group in an experiment where the variable being tested is isolated and environmental factors are kept constant.

Placebo Effect

Psychological phenomenon where participants report improvements believing they received treatment.

Double-Blind Testing

Study where neither participants nor researchers know who receives the treatment or placebo.