Earth Science · Kindergarten–Grade 8 · Quick reference
Earth Science(Rocks · Water · Sky)
Rocks, minerals and soil, the water cycle, clouds and weather, the earth’s layers, plates, volcanoes and earthquakes, reading rock layers and the Flood as the course teaches it, the solar system, seasons, the moon and stars, and the resources, maps and careers of grade 8.
1Rocks, Minerals & SoilK–8 · the ground under our feet
| Kind | How it forms | Examples |
|---|---|---|
| Igneous | melted rock (magma, lava) cools and hardens | granite, basalt, obsidian, pumice |
| Sedimentary | sediments settle in layers and cement | sandstone, shale, limestone, conglomerate, coal |
| Metamorphic | rock changed by heat and pressure | marble (from limestone), slate (from shale), quartzite, gneiss |
Sort a rock
Size: boulder, cobble, pebble, sand, silt, clay. Test: color, streak, luster (shiny or dull), hardness, layers, grains, fizz with vinegar (limestone). Label every specimen: where, when, who.
| # | Mineral | Test | # | Mineral | Test |
|---|---|---|---|---|---|
| 1 | talc | fingernail | 6 | feldspar | steel file |
| 2 | gypsum | fingernail | 7 | quartz | scratches glass |
| 3 | calcite | copper penny | 8 | topaz | |
| 4 | fluorite | knife | 9 | corundum | |
| 5 | apatite | knife | 10 | diamond | only diamond |
Minerals
A mineral is a natural, solid, non-living substance with a fixed makeup and crystal shape; rocks are made of minerals. Ore is rock worth mining for its metal. Gold is dense (19.3 g/cm³): it sinks in the pan (Sutter’s Mill, 1848).
Soil
- Soil = broken rock + humus (rotted plants and animals) + air + water + living things. Worms loosen and feed it.
- Horizons: O (leaf litter), A (topsoil, dark), B (subsoil), C (broken bedrock), then bedrock.
- Sand drains fast, clay holds water and molds, loam mixes both and grows the best crops.
- Keep soil: contour plowing, cover crops, windbreaks. The Dust Bowl (1930s) blew bare topsoil away.
Fossils
Remains or traces of once-living things buried quickly in sediment: shells, bones, prints, amber. Mary Anning found sea reptiles at Lyme Regis (1811). Fossil seashells sit on mountaintops; fossil graveyards hold thousands of animals buried together.
2Water & WeatherK–8 · the water cycle, clouds, wind, storms
The water cycle
- Evaporation: the sun turns liquid water into vapor.
- Condensation: vapor cools into droplets: clouds, dew, fog.
- Precipitation: rain, snow, sleet, hail fall.
- Collection: water runs into streams, rivers, lakes, the sea, or sinks into the ground (springs, wells, aquifers).
Water freezes at 32 °F / 0 °C and boils at 212 °F / 100 °C. Ice floats. About 71% of the earth is covered by water; 97% of it is salty sea.
Rivers
Source (spring or snowmelt) → tributaries join → floodplain → delta at the mouth. Running water rounds stones, carves canyons and builds deltas (the Nile). Waterfalls retreat upstream (Niagara). Glaciers are rivers of ice that scrape valleys and drop boulders.
| Name | Latin | Look | Weather |
|---|---|---|---|
| Cirrus | curl | high, wispy, icy | fair, change coming |
| Cumulus | heap | puffy, flat base | fair; towering ones storm |
| Stratus | layer | gray sheet | drizzle, overcast |
| Nimbus | rain | dark, heavy | rain or snow (cumulonimbus = thunderstorm) |
| Tool | Measures |
|---|---|
| thermometer | temperature |
| barometer | air pressure (falling = storm) |
| rain gauge | rainfall in inches |
| wind vane | wind direction (named by where it comes from) |
| anemometer | wind speed |
| hygrometer | humidity |
Weather and climate
- Weather is today; climate is the usual pattern over years.
- Warm air rises; cool air sinks. Wind is air moving from high to low pressure. Sea breezes blow onshore by day.
- Fronts: cold front = thunderstorms then clear; warm front = long steady rain.
- Lightning is a giant spark; thunder follows (5 seconds ≈ 1 mile). Go indoors.
- Tornado: go low, inside, away from windows. Hurricane: warm-ocean storm; eye in the middle; leave when told.
- A rainbow is sunlight bent by raindrops: red outside, violet inside.
Red sky at night
“Red sky at night, sailors’ delight; red sky in the morning, sailors take warning” (Matthew 16:2–3). Weather usually moves west to east.
3Inside the Earth: Plates, Volcanoes, Earthquakesgrades 6–7 · the dynamic earth
| Layer | State | Note |
|---|---|---|
| Crust | solid rock | 5–40 mi thick; thinnest under oceans |
| Mantle | hot, slowly flowing rock | most of the earth’s volume |
| Outer core | liquid iron and nickel | makes the magnetic field |
| Inner core | solid iron | Inge Lehmann found it from earthquake waves, 1936 |
Plates
The crust is broken into plates that move. Divergent: pull apart, new crust (Mid-Atlantic Ridge, Iceland). Convergent: collide, mountains or trenches (Himalaya: India pushes into Asia). Transform: slide past (San Andreas). Wegener’s puzzle fit (1912); the course also studies catastrophic plate tectonics (Baumgardner) as a Flood model.
| Type | Shape | Example |
|---|---|---|
| Shield | broad, gentle, runny lava | Hawaii |
| Cinder cone | small, steep, cinders | Parícutin grew in a cornfield, 1943 |
| Composite | tall, layered, explosive | Vesuvius (A.D. 79), Mount St. Helens (1980) |
Mountains
Rock folds (anticline up, syncline down) and faults (breaks). The Himalaya, Alps and Appalachians are folded; some bent layers show no cracking (Sideling Hill).
Earthquakes
- Rock snaps along a fault: the focus is the break underground, the epicenter the point above it.
- P waves arrive first (push-pull); S waves second (side to side); surface waves do the damage. A seismograph records them.
- Magnitude (Richter, moment): each whole number ≈ 10× the shaking and ≈ 32× the energy. Lisbon (1755) started the science.
- A tsunami is a harbor wave from a sea-floor quake: if the water pulls back, run to high ground (Kamaishi, 2011).
- Buildings survive by flexing: Taipei 101’s steel ball. Drop, cover, hold on.
Crust, mantle, core
Like a peach: thin skin (crust), thick flesh (mantle), hard pit (core). A compass needle points along the magnetic field made in the outer core.
4Reading the Rocks: Layers, Erosion & the Floodgrades 6–8 · earth history as the course teaches it
Steno’s principles (1669)
- Superposition: in undisturbed layers the bottom one was laid first.
- Original horizontality: sediments settle in flat layers.
- Lateral continuity: a layer once stretched across the whole basin.
- Cross-cutting: a fault or dike is younger than the layers it cuts.
Weathering, erosion, deposition
Weathering breaks rock in place (ice wedging, roots, acid rain, heat). Erosion carries pieces away (water, wind, ice, gravity). Deposition drops them (deltas, dunes, moraines). Canyon Lake Gorge (2002) was cut in days by a flood.
Catastrophe or slow change?
- Uniformitarianism (Hutton, Lyell): the present slow rates explain the past. Catastrophism (Cuvier, Bretz’s Scablands): great floods shaped the land quickly.
- The course reads Genesis 6–9 as history: a year-long global Flood that laid down vast layers, buried fossil graveyards, and was followed by one Ice Age (Agassiz saw glacier marks, 1837).
- Flat gaps between layers, coal seams, folded-while-soft rock and worldwide flood legends are weighed as evidence.
Dating methods
Radioactive atoms decay with a half-life (half the parent remains each half-life). A radiometric age rests on three assumptions: the starting amounts, no gain or loss, and a constant rate. Discordant dates (Mount St. Helens dacite, 1996) and carbon-14 in diamonds and coal are the course’s test cases. Old-earth and secular readings are summarized fairly in grade 8.
Dinosaurs
Reptile kinds known from bones, eggs and nests; sorted by hips, teeth and feet. Behemoth (Job 40) and dragon legends are read alongside. Soft tissue in bone (2005) is discussed. Living fossils (coelacanth, 1938) look like their fossils.
Ice Age
Glaciers carved U-shaped valleys, left moraines and erratic boulders, and lowered sea level. Woolly mammoths lived along the ice edge. Ice cores are read by counting layers.
Oldest on the bottom
A stack of pancakes: the first one poured is on the bottom. Anything that cuts the stack came after it.
5Sun, Moon & Starsgrades K–5 · the sky
| Planet | Kind | Note |
|---|---|---|
| Mercury | rocky | closest, cratered |
| Venus | rocky | hottest, thick clouds |
| Earth | rocky | liquid water, one moon |
| Mars | rocky | red, two tiny moons |
| Jupiter | gas giant | largest, Great Red Spot |
| Saturn | gas giant | bright rings |
| Uranus | ice giant | Herschel, 1781; tipped on its side |
| Neptune | ice giant | farthest, windy |
Day, year, seasons
- Rotation on its axis: 24 hours, day and night; shadows swing and shorten toward noon (sundial).
- Revolution around the sun: 365¼ days, so every fourth year is a leap year.
- The axis tilts 23.5°; the half tipped toward the sun has summer. Solstices about June 21 and December 21; equinoxes about March 20 and September 22.
- Time zones: 24 zones of 15° each, set by the railroads in 1883.
- Eratosthenes measured the earth with a shadow (c. 240 B.C.): about 24,900 miles around. Julian (46 B.C.) and Gregorian (1582) calendars.
Kepler and Newton
Planets move in ellipses with the sun at one focus, sweep equal areas in equal times, and farther planets take longer (T² ∝ a³). Newton: the same gravity that drops an apple holds the moon in orbit.
The moon
- Phases in 29½ days: new → waxing crescent → first quarter → waxing gibbous → full → waning gibbous → third quarter → waning crescent. We see the sunlit half from different angles.
- Solar eclipse: moon between sun and earth. Lunar eclipse: earth’s shadow on the moon.
- Tides: two highs and two lows a day, pulled by the moon; spring tides at new and full moon, neap tides at the quarters.
- Galileo saw mountains on the moon (1609); Apollo 11 landed July 20, 1969.
Stars
- Polaris, the North Star, sits over the pole: find it from the Big Dipper’s pointer stars. The Southern Cross guides the south.
- Star colors tell heat: blue-white hottest, yellow (our sun), red coolest. Orion and the Pleiades are named in Job 38:31.
- A light-year is the distance light travels in a year, about 5.9 trillion miles. Telescopes: refractor (lenses), reflector (mirror), Hubble and Webb in space.
6Resources, Maps & Careersgrade 8 · the ground people work
Water underground
Rain sinks into porous rock and sand, an aquifer; its top is the water table. A well reaches below it; a spring is where it surfaces. Jacob’s well (John 4). Western water rights: first in time, first in right.
Fuels
Coal, oil and natural gas come from buried plants and sea life. Oil and gas collect in traps, porous reservoir rock capped by shale. Drake’s well (1859), Spindletop (1901). A barrel refines into gasoline, diesel, jet fuel, asphalt and plastics.
Mining
Open-pit (Bingham Canyon) for shallow ore, underground shafts for deep seams. Mine Act (1977) after Monongah (1907); reclamation law (SMCRA, 1977) puts the land back. Every tool, wire and brick began as rock.
Materials (K)
Wood, stone, metal, glass, plastic, cloth: sort by property (hard, soft, bends, floats, waterproof) and pick the right material for the job.
Maps
- Topographic maps: contour lines join equal heights; close lines mean steep ground; the contour interval is the step between lines.
- William Smith drew the first geological map (1815) by tracing rock layers and their fossils.
- GIS stacks map layers (roads, rock, water, elevation) by coordinates; QGIS is free. USGS maps show your county’s geology.
Careers
Geologist, driller, miner, soil scientist, well driller, surveyor, meteorologist (National Weather Service since 1870; first tornado forecast 1948), storm chaser, aviation weather. Interview one; keep a field notebook.