Year 8 Science: Earth Moves, Rocks, Minerals, and Plate Tectonics

Comprehensive vocabulary flashcards covering Earth's internal structure, rock types, mineral properties, plate tectonics, seismic hazards, and ethical archaeological considerations.

Crust

The rocky, brittle, outermost layer of Earth, ranging from $5\text{--}70\,\text{km}$ in thickness.

Mantle

Earth's thickest layer, measuring $2900\,\text{km}$ thick; composed of dense rock where approximately $1\%$ can flow like a thick fluid over long geological time scales.

Outer Core

A liquid layer located below the mantle, measuring $2200\,\text{km}$ thick and composed primarily of molten iron and nickel.

Inner Core

A solid ball composed mostly of iron and nickel located at the centre of Earth, with a thickness of $1250\,\text{km}$.

Scientific Model

A representation of a part of the natural world that is difficult to observe directly, such as using a hard-boiled egg or sponge cake to study Earth's structure.

Mineral

A naturally occurring pure substance with an orderly crystal structure, serving as a fundamental building block of rocks.

Hardness

A physical property describing how easily a mineral or material can be scratched by another substance.

Mohs Hardness Scale

A standard scale rating the scratch resistance of minerals from 1 (talc) to 10 (diamond).

Streak

The colour of the powdered mineral left behind when it is scraped across an unglazed porcelain streak plate.

Lustre

The appearance of light reflecting from the surface of a mineral, described by terms such as vitreous, metallic, or dull.

Cleavage

The tendency of a mineral to split along smooth, flat planes determined by zones of weakness in its crystal structure.

Conchoidal Fracture

A smooth, curved fracture resembling the surface of a semicircular shell, commonly seen in broken glass and obsidian.

Vitreous

A glassy appearance or lustre displayed by certain minerals such as quartz.

Sedimentary Rock

A rock formed by the compaction and cementation of mineral particles or sediments, typically characterized by visible layers, pores, and occasionally fossils.

Igneous Rock

A rock formed by the cooling and solidification of molten rock (magma or lava), characterized by non-porous textures and interlocking crystals pointing in multiple directions.

Metamorphic Rock

A rock transformed from an existing rock by intense heat and pressure without fully melting, often displaying aligned crystals or banded foliation.

Porous

A physical property describing a rock containing open spaces or gaps between its grains that allow fluids to absorb and pass through.

Non-porous

A physical property describing a rock with tightly interlocking grains or crystals that prevent water from permeating.

Tectonic Plate

A large, rigid slab of Earth's lithosphere (~$125\,\text{km}$ thick), consisting of the crust and uppermost mantle, that moves across the planet's surface.

Continental Drift

The hypothesis proposed by Alfred Lothar Wegener stating that Earth's continents were once joined together and subsequently drifted across the planet's surface.

Slab Pull

The major driving force of plate motion where a colder, denser tectonic plate sinks into the mantle under gravity, dragging the trailing plate along with it.

Ridge Push

A force driving plate movement wherein gravity causes elevated, newly formed oceanic crust at mid-ocean ridges to push older lithosphere outward.

Convection Current

Thermal circulation of molten or ductile rock in the mantle that acts like a conveyor belt, carrying overlying tectonic plates.

Focus

The point deep inside Earth where an earthquake ruptures and initial seismic shockwaves originate.

Epicentre

The point on Earth's surface positioned directly above the focus of an earthquake.

Fault Line

A fracture in Earth's crust along which significant rock movement and ground displacement take place.

Earthquake Magnitude

A measurement characterizing the relative size and total energy released by an earthquake; each whole-number step corresponds to a tenfold increase in measured amplitude and roughly $32$ times more energy released.

Seismic Isolator

A protective device featuring flexible rubber pads placed between a building and its concrete foundation to absorb ground vibrations and allow gentle swaying during seismic shaking.

Tsunami

A series of high-speed ocean waves produced by underwater earthquakes or volcanic eruptions, derived from the Japanese words 'tsu' (harbour) and 'nami' (wave).

Hotspot

An anomalously hot region within Earth's mantle that generates volcanic activity in the middle of a tectonic plate, an idea introduced by John Tuzo Wilson.

Transform Fault

A plate boundary where tectonic plates slide horizontally past one another, recognized by John Tuzo Wilson as a missing link in plate tectonic theory.

Seafloor Spreading

The process proposed by Harry Hammond Hess where volcanic activity at mid-ocean ridges produces new oceanic crust that moves outward from the ridge crest.

Cultural Ownership

The ethical principle recognizing that cultural knowledge, sacred heritage, and ancestral artefacts belong specifically to Indigenous communities and Traditional Owners.