Earth Science 11

Minerals are identified by testable physical properties: hardness (scratch test against the Mohs scale), lustre (metallic vs. non-metallic shine), cleavage/fracture (the pattern a mineral breaks along), colour, and streak (the colour of its powder, which is more reliable than surface colour).

Surface processes break rock down and move the pieces: weathering breaks rock into smaller fragments (mechanically or chemically), erosion transports those fragments, and deposition settles them somewhere new — the raw material for future sedimentary rock.

Economic feasibility of extracting a resource depends on price, concentration/grade, accessibility, and environmental concerns — a rich but hard-to-reach deposit may not be worth mining even at a high market price.

Minerals form in each of the three rock environments — crystallizing directly from magma in igneous rock, precipitating or being deposited in sedimentary rock, or recrystallizing under heat and pressure in metamorphic rock — so the same mineral can turn up in more than one rock family.

Internal processes rebuild and transform rock using heat and pressure: burial and cementation turn loose sediment into sedimentary rock; heat and pressure without melting transform any rock into metamorphic rock; and melting followed by cooling/crystallization creates igneous rock (either underground as intrusive rock, or at the surface as extrusive/volcanic rock).

Continental fit and matching fossils/rock sequences across now-separated continents (e.g. matching fossil species and rock layers on the coasts of South America and Africa) suggest those continents were once joined.

Heat from within Earth's core and from excess radioactivity within the mantle powers mantle convection currents — hot mantle material rises, spreads, cools, and sinks in a continuous circulation pattern, dragging the rigid plates above along with it.

First Peoples oral histories along the BC coast record specific, real geologic events — including the great Cascadia subduction zone earthquake and tsunami — passed down across many generations with details (timing, shaking, flooding) that match the physical geologic evidence found in sediment layers.

Seafloor magnetic striping — symmetric bands of alternating magnetic polarity on either side of mid-ocean ridges — records seafloor spreading over time and gives geologists a way to measure the rate and direction of plate motion directly.

Ridge push occurs at mid-ocean spreading centres, where newly formed oceanic crust is elevated and cools/thickens as it moves away from the ridge, causing it to slide downhill under gravity and push the plate along.

Evaporation (liquid water becoming water vapour, driven by solar energy, mostly from the oceans) and condensation (vapour becoming liquid droplets, forming clouds) are the phase-change engine of the cycle.

Natural causes of atmospheric change include volcanic outgassing (releasing carbon dioxide, sulfur dioxide, and water vapour) and biological activity (photosynthesis historically built up atmospheric oxygen over geologic time; respiration and decomposition release carbon dioxide).

Air masses form with distinct temperature and moisture characteristics depending on where they originate; when air masses of different temperature or pressure meet, the boundary (a front — cold, warm, or occluded) often produces active weather.

Local air currents (like an on-shore breeze, caused by land heating and cooling faster than water) and global air currents (like the jet stream, a fast-moving band of upper-atmosphere wind driven by temperature contrasts) both move energy and moisture across a region or the whole planet.

Incoming solar radiation is partly reflected back to space immediately (by clouds, ice, and light-coloured surfaces — a surface's reflectivity is called its albedo) and partly absorbed by the surface and atmosphere, converting to heat.

Fresh water sources — rivers, glaciers, groundwater — supply most human and ecosystem needs but represent a small fraction of Earth's total water, making them a genuinely limited resource despite appearing abundant.

First Peoples knowledge of water resources is built from generations of close observation of specific rivers, lakes, and watersheds — their seasonal flow patterns, fish runs, and water quality — providing detailed, place-based environmental knowledge.

Remote sensing methods — sonar (sound-based mapping) and satellite altimetry — let scientists map large-scale ocean floor features (mid-ocean ridges, trenches, seamounts) and ocean surface properties (temperature, height) without physically visiting every location.

Water density increases as salinity increases and as temperature decreases; denser water sinks while less dense water rises, and this density difference is the fundamental driver of large-scale (thermohaline) ocean circulation.

Locally, large bodies of water moderate nearby temperatures (water heats and cools more slowly than land, reducing daily/seasonal extremes) and drive on-shore breezes as land and water heat unevenly through the day.

The nebular hypothesis proposes that the solar system formed from a large, collapsing cloud of gas and dust (a nebula), pulled inward by gravity over time.

Earth's position and temperature allow liquid water to persist at the surface — a condition considered essential for life as we understand it, and one most other solar system bodies lack.

Stellar classification sorts stars by measurable properties — chiefly temperature and colour (hot blue-white stars vs. cooler red stars) — and plots them on the Hertzsprung-Russell (H-R) diagram, which reveals patterns linking a star's temperature to its true luminosity.

Tides result from the gravitational pull of the moon (and, to a lesser extent, the sun) on Earth's oceans; Earth's rotation carries locations through the tidal bulges, producing the daily cycle of high and low tides.

Seasonal variation results from Earth's tilted axis relative to its orbit around the sun: the hemisphere tilted toward the sun receives more direct, concentrated sunlight and longer days (summer), while the other hemisphere receives it at a shallow angle (winter) — the changing distance to the sun over the year is NOT the cause.

Significant figures are the digits in a measurement that carry real information about precision — including all certain digits plus one estimated digit — and the number of significant figures should match what the measuring instrument can actually resolve.

Every measurement has an associated uncertainty (often written as ± a value) reflecting the limits of the instrument and the observer — reporting a bare number without uncertainty hides how confident that measurement really is.

Rounding rules keep calculated results honest: when combining measurements (adding, multiplying), the result cannot claim more precision than the least precise measurement that went into it.

Accuracy (how close a measurement is to the true value) and precision (how consistent repeated measurements are with each other) are related but different — a set of measurements can be precise (tightly clustered) without being accurate (close to the true value).

Recording too many digits (false precision) overstates how well something was actually measured — a rock sample massed on a scale that reads to the nearest gram should not be reported with decimal places the scale cannot support.