https://teddyrookbook.com/earth-and-space/geology/Recent content in Geology on Teddy Rook Bookhttps://teddyrookbook.com/img/share.jpghttps://teddyrookbook.com/img/share.jpgHugoenhttps://teddyrookbook.com/earth-and-space/geology/earth-formation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/earth-formation/Earth grew from colliding rock and metal about 4.54 billion years ago and, while hot, sorted itself by density into core, mantle and crust. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/seismic-interior/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/seismic-interior/S waves can't cross the liquid outer core and P waves bend at its edge, leaving shadow zones that map the core. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/geothermal-gradient/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/geothermal-gradient/Temperature rises about 25 °C per kilometer in the upper crust, fed by heat left from Earth's formation and by radioactive decay. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/isostasy/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/isostasy/Crust floats on the mantle like ice on water, so high mountains have deep roots and land rises when an ice sheet melts. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/paleomagnetism/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/paleomagnetism/Earth's field flips now and then, and iron-rich minerals in cooling lava record its direction, building a timeline of reversals. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/crystal-structure/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/crystal-structure/A mineral is ions stacked in a repeating pattern, and ions of similar size and charge can trade places, so a mineral's makeup can vary. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/silica-tetrahedron/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/silica-tetrahedron/One silicon bonded to four oxygens, SiO₄ with a charge of −4, is the building block of most minerals in the crust. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/silicate-families/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/silicate-families/Tetrahedra link as singles, chains, double chains, sheets or 3-D frameworks, which sets each mineral's silicon-to-oxygen ratio and how it breaks. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/nonsilicates/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/nonsilicates/Sort minerals by their negative ion: carbonates (CO₃), oxides (O), sulfides (S), sulfates (SO₄), halides (Cl, F) and native elements. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/melting/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/melting/Rock in the mantle melts when the pressure drops, when water is added, or when hot magma heats the crust around it. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/bowen-series/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/bowen-series/As magma cools, minerals crystallize in order: olivine and calcium-rich feldspar first, quartz last. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/magma-composition/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/magma-composition/Magmas range from mafic (low in silica, hot, runny and dark) to felsic (high in silica, cooler, sticky and light). Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/igneous-classification/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/igneous-classification/Name an igneous rock from its texture and composition: granite and rhyolite, diorite and andesite, gabbro and basalt. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/intrusions/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/intrusions/Magma that cools underground forms batholiths, dikes that cut across layers and sills that slip between them. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/eruption-styles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/eruption-styles/Viscosity and gas decide whether magma oozes out as lava or blasts out as ash; the VEI rates eruptions by volume, ten times more per step. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/volcanic-hazards/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/volcanic-hazards/Pyroclastic flows, lahars, ash, gases and lava each threaten in their own way; swelling ground, gas and small earthquakes can give warning. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/chemical-weathering/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/chemical-weathering/Feldspar turns to clay, iron minerals rust and calcite dissolves, while quartz resists and piles up as sand. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/grain-size/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/grain-size/Sort sediment by size, from clay under 1/256 mm to boulders over 256 mm, and use the phi scale, φ = −log₂ d. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/sediment-transport/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/sediment-transport/Faster water moves bigger grains; the Hjulström diagram shows when a grain is picked up, carried or dropped. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/sorting-rounding/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/sorting-rounding/The farther sediment travels, the better sorted and rounder it gets and the more of it is quartz. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/sedimentary-classification/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/sedimentary-classification/Name clastic rocks by grain size and shape (conglomerate, breccia, sandstone, shale) and chemical and biochemical rocks by makeup (limestone, rock salt, chert, coal). Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/sedimentary-structures/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/sedimentary-structures/Cross-beds, ripple marks, mud cracks and graded beds show current direction, waves, drying out and which way was up. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/depositional-environments/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/depositional-environments/Match rocks and structures to the place they formed: river, delta, beach, reef, deep sea, desert dunes or glacier. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/pressure-depth/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/pressure-depth/Pressure grows by about 26 MPa for each kilometer of rock overhead (P = ρgh), and temperature rises along the geotherm. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/metamorphic-grade/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/metamorphic-grade/As heat and pressure rise, shale becomes slate, phyllite, schist and then gneiss, and index minerals like garnet appear in order. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/metamorphic-classification/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/metamorphic-classification/Name a metamorphic rock by its foliation and its parent: marble from limestone, quartzite from sandstone, gneiss from granite or shale. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/metamorphic-settings/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/metamorphic-settings/Contact metamorphism bakes rock beside magma, regional metamorphism comes with mountain building, and subduction makes high-pressure, low-temperature rocks. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/stress-strain/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/stress-strain/Rocks are squeezed, stretched or sheared; near the surface they break (brittle), while deep and hot they bend (ductile). Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/folds/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/folds/Folds arch up (anticlines) or sag down (synclines); once eroded, an anticline shows its oldest rocks in the middle. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/faults/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/faults/Name the hanging wall and footwall and read the slip: pulling apart makes normal faults, squeezing makes reverse and thrust faults, and shearing makes strike-slip faults. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/strike-dip/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/strike-dip/Strike is the compass direction of a level line on a tilted layer, dip is its downward tilt, and with trigonometry they give how deep the layer lies. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/steno-principles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/steno-principles/Original horizontality, lateral continuity, inclusions and the order of fossils extend superposition to read any outcrop. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/unconformities/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/unconformities/A buried erosion surface marks missing time: an angular unconformity, a nonconformity or a disconformity. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/correlation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/correlation/Match layers from place to place by rock type, by key beds such as volcanic ash, and by index fossils. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/geologic-history/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/geologic-history/Put a cross-section's events in order: deposition, folding, faulting, intrusion, erosion and more deposition. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/radiometric-dating/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/radiometric-dating/From the ratio of daughter to parent atoms, find how many half-lives have passed: a ratio of 1 means one half-life, 3 means two, 7 means three. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/isotope-systems/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/isotope-systems/Match the clock to the job: carbon-14 for recent remains, potassium–argon and uranium–lead for igneous rock millions to billions of years old. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/bracketing-ages/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/bracketing-ages/Date a sedimentary layer by the dated igneous rocks around it: younger than what lies below it, older than what cuts it or covers it. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/earth-history/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/earth-history/Place the big events on the time scale: the oldest minerals, first life, oxygen in the air, the Cambrian explosion and the great mass extinctions. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/magnetic-stripes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/magnetic-stripes/Match seafloor stripes to the reversal timeline to find how fast a ridge spreads, as a half rate or a full rate. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/gps-plate-motion/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/gps-plate-motion/GPS stations move millimeters to centimeters a year; subtracting their velocity vectors shows how two plates move relative to each other. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/driving-forces/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/driving-forces/Sinking slabs pull plates, high ridges push them, and the mantle convects beneath; the pull of sinking slabs is the largest force. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/subduction-zones/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/subduction-zones/The denser plate sinks, earthquakes trace the slab hundreds of kilometers down, and water from the slab melts the mantle above to feed arc volcanoes. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/collisions-and-rifts/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/collisions-and-rifts/Continents are too buoyant to sink far, so they crumple into high mountains when they meet and stretch into rift valleys when they split. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/transform-faults/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/transform-faults/Transform faults offset mid-ocean ridges and let plates slide past each other, and only the part between the ridge segments is active. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/wilson-cycle/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/wilson-cycle/Oceans open and close in a cycle (rift, young ocean, wide ocean, subduction, closing and collision), with supercontinents like Pangaea in between. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/elastic-rebound/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/elastic-rebound/Rock on both sides of a locked fault bends slowly, then snaps back in an earthquake; slip rate and slip per quake give the average time between quakes. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/locating-earthquakes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/locating-earthquakes/P waves outrun S waves, so the gap between their arrivals grows with distance: d = Δt·vP·vS/(vP − vS). Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/epicenter/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/epicenter/Draw a circle of the right distance around each of three stations; the epicenter is where all three circles meet. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/moment-magnitude/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/moment-magnitude/Magnitude grows with the logarithm of the fault's area times its slip, and each step up means about 32 times more energy. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/intensity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/intensity/Intensity measures the shaking at one place on the Modified Mercalli scale; it depends on distance, depth and soft ground, not only on magnitude. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/earthquake-odds/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/earthquake-odds/Turn a yearly chance into the chance of at least one event in n years: 1 − (1 − p)ⁿ. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/tsunamis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/tsunamis/A sudden jolt of the seafloor lifts the whole water column; the wave crosses deep ocean as fast as a jet (v = √(gd)) and slows and grows tall near shore. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/mass-wasting/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/mass-wasting/A slope fails when the downhill pull beats the friction and strength holding it; water and steeper slopes tip the balance. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/stream-flow/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/stream-flow/A stream's gradient is its drop per distance, and its discharge is width × depth × speed, in cubic meters per second. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/river-landforms/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/river-landforms/Rivers wear away the outside of bends and build on the inside, spread floodplains, and cut down toward base level. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/flood-frequency/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/flood-frequency/Rank a river's yearly peak flows to find recurrence intervals; a 100-year flood has a 1% chance of happening in any year. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/groundwater-flow/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/groundwater-flow/Groundwater flows from high head to low head, and Darcy's law, Q = K·A·Δh/L, tells how much. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/glaciers/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/glaciers/A glacier gains snow up high and loses ice down low; its end advances or retreats with the balance, but the ice always flows downhill. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/ore-deposits/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/ore-deposits/Ores are rare places where geology concentrated a metal; magma, hot water, weathering, evaporation and rivers can all do it. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/fossil-fuels/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/fossil-fuels/Buried remains of tiny sea life cook into oil at about 60 to 120 °C and collect under a seal in a trap, while buried swamp plants become coal. Geology · Earth & Space Ladderhttps://teddyrookbook.com/earth-and-space/geology/resource-reserves/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/earth-and-space/geology/resource-reserves/Reserves are the part of a resource that can be produced at a profit today, so the years they last change with price, technology and discovery. Geology · Earth & Space Ladder