96 Geology Trivia Questions and Answers
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Easy Geology Trivia Questions
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What cave formation grows upward from the floor?
Stalagmite
It forms as mineral-laden water drips from the cave roof and deposits calcite on the floor below, building upward layer by layer. Growth is so slow that many stalagmites take thousands of years to reach just a few centimeters tall.
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Which two metals make up most of Earth's core?
Iron and nickel
Earth's core is composed primarily of iron and nickel, unlike the rocky silicate materials that dominate the mantle and crust.
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Which layer of Earth stays solid even though it is the hottest part of the planet?
Inner core
Pressure at Earth's center is so extreme, several million times that at the surface, that it keeps iron and nickel locked into a solid even though the temperature there rivals the surface of the Sun.
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Which major compositional layer of Earth is thinnest?
Crust
The crust is a thin rocky shell compared with the mantle and core.
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What surface location lies directly above an earthquake's focus?
Epicenter
The epicenter is the point on Earth's surface above the focus.
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What directly causes the shaking of an earthquake?
A sudden slip on a fault
An earthquake occurs when stress overcomes friction on a fault and the rocks suddenly slip, releasing energy as seismic waves.
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What geological process carries weathered rock and sediment from one place to another?
Erosion
Erosion transports weathered rock and sediment from one place to another, often through water, wind, ice, or gravity. Over time, it can carve valleys and reshape coastlines.
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The word 'volcano' comes from Vulcan, the Roman god of what?
Fire and the forge
Vulcan was the Roman god of fire and metalworking. The Aeolian island of Vulcano, thought to sit above his forge, passed its name on to every mountain that erupts.
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What waterway chiefly carved the Grand Canyon?
Colorado River
The Colorado River is chiefly responsible for carving the Grand Canyon.
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A preserved footprint is classified as what?
Trace fossil
A preserved footprint records an organism's activity, making it a trace fossil. The alternatives are genuine fossil categories.
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In which type of material are fossils most often found?
Sedimentary rock
Fossils form most often in sedimentary rock, because mud, sand and silt settle gently over remains and bury them before they rot away. Rock made by heat or crushing pressure destroys whatever structure was there.
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What process widens cracks when water freezes and expands?
Frost wedging
Water expands by about 9 percent as it freezes, and the resulting pressure is enough to pry rock apart along existing cracks. It does most of its damage in climates where the temperature crosses freezing point repeatedly, such as alpine and subpolar regions, rather than in places that are simply cold.
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Which common building stone is a coarse-grained igneous rock?
Granite
Granite forms as magma cools slowly deep underground, which gives the crystals time to grow large. That is why a polished slab shows visible interlocking grains of quartz, feldspar and mica.
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Which rock can form when limestone is changed by heat and pressure?
Marble
Heat and pressure can metamorphose limestone into marble, changing its texture and mineral structure without melting it completely.
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Where is new oceanic crust most commonly created?
At a mid-ocean ridge
New oceanic crust forms most commonly at mid-ocean ridges, where tectonic plates diverge and magma cools. The alternatives are real oceanic tectonic settings but are less common or do not typically produce new crust.
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What is a mineral's tendency to split along flat planes called?
Cleavage
Cleavage reflects weaknesses in a crystal lattice.
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What ranks minerals by resistance to scratching?
Mohs scale
The Mohs scale ranks minerals by their resistance to scratching. It ranges from talc at 1 to diamond at 10, though the scale is relative rather than evenly spaced.
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Which mineral is the softest standard on the Mohs scale?
Talc
Talc has Mohs hardness 1.
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What is molten rock called after it reaches Earth's surface?
Lava
Molten rock beneath Earth's surface is magma; once it erupts onto the surface, it is called lava.
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What type of rock is obsidian?
Volcanic glass
Obsidian is volcanic glass formed when viscous magma erupts as lava and cools rapidly, preventing crystals from forming.
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What is a natural concentration of minerals valuable enough to extract called?
Ore
Ore contains economically recoverable minerals or metals.
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What was the ancient supercontinent called before today's continents separated?
Pangaea
Pangaea was a single ancient supercontinent that gradually broke apart as the continents moved into their present positions.
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New seafloor is created along mid-ocean ridges. Which kind of plate boundary makes it?
Divergent boundary
A divergent boundary forms where tectonic plates move away from each other. As they separate, magma rises to fill the gap and can create new crust, especially along underwater mid-ocean ridges.
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At a convergent boundary between oceanic and continental crust, what happens?
The oceanic plate subducts
Oceanic crust is denser than continental crust, mostly basalt rather than granite, so it dives into the mantle instead of crumpling upward. This is the mechanism that built the Andes and carved deep trenches like the one off the coast of Chile.
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At what kind of tectonic setting do plates mainly slide horizontally past one another?
Transform boundary
At a transform boundary, tectonic plates slide horizontally past one another. This motion often produces earthquakes, such as those along California’s San Andreas Fault.
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What makes pumice buoyant?
Trapped gas bubbles
Pumice can float because trapped, isolated gas bubbles make it less dense than water. If water eventually fills those tiny pockets, the pumice sinks.
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What landform can build up where a river drops its sediment at the mouth?
Delta
Where a river meets the sea or a lake it slows suddenly and can no longer carry its load, so sand and silt settle out and the channel splits into branches picking their way across the deposit. The fan of land that results is a delta, named after the Greek letter for the triangular shape of the Nile's.
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Which sedimentary rock forms when grains between about 0.06 and 2 mm across are cemented together?
Sandstone
Sand grains can accumulate, compact, and become cemented into sandstone; gravel forms conglomerate and mud can form shale.
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Which seismic disturbance travels fastest?
P wave
P waves travel fastest because they move through the Earth by compressing and expanding material in the direction of travel. They can pass through solids and liquids, unlike S waves, which cannot travel through liquids.
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Which agent typically carves broad U-shaped valleys?
Glaciers
Moving glaciers can scour valley sides and floors into broad U-shaped profiles as they erode the landscape.
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Volcanic ash is made mostly of what?
Tiny fragments of rock, mineral and glass
Volcanic ash is pulverised rock: fragments of rock, mineral crystals and volcanic glass under 2 millimetres across, thrown out when an eruption shatters magma. It is hard, abrasive and does not dissolve in water, which is why it ruins jet engines and collapses roofs.
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A volcano's conduit ends at the surface in which feature?
Vent
A vent is the opening at the surface where lava, ash and gas escape. A volcano usually has a central vent at the summit, and can open smaller flank vents on its sides.
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What type of volcano has broad, relatively gentle slopes?
Shield volcano
Shield volcanoes are built by runny basaltic lava that travels a long way before it cools, spreading into a low, wide dome rather than a cone. Mauna Loa in Hawaii is the classic example.
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Mount Fuji, Vesuvius and Mount St Helens are all steep cones built from alternating lava and tephra. What type of volcano is that?
Stratovolcano
A stratovolcano, also called a composite volcano, is built up from alternating layers of lava flows and tephra, the ash and fragments an eruption throws out. The mix stacks into the steep classic cone of Fuji, Vesuvius and Mount St Helens.
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What is the breakdown of rock at Earth's surface without transport called?
Weathering
Weathering breaks rock down in place; erosion moves the products.
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Which diamond is the largest gem-quality rough diamond ever found, at 3,106 carats?
The Cullinan Diamond
A mine surface manager found the stone at the Premier mine in South Africa in January 1905 and was given a bonus for the discovery. It was later cut into nine major stones, including the pear-shaped Cullinan I, or Great Star of Africa, which is now set in the British Sovereign's Sceptre.
Medium Geology Trivia Questions
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What is a fast-moving, ground-hugging cloud of hot gas, ash and rock fragments from a volcano called?
A pyroclastic flow
A pyroclastic flow races downhill at hundreds of kilometres an hour and is the deadliest volcanic hazard. A lahar is the mud version, driven by water.
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What volcanic rock makes up much of oceanic crust?
Basalt
Basalt is a dark, fine-grained lava rock that erupts along the mid-ocean ridges and cools fast in seawater. It paves almost the whole seafloor, which makes it the most abundant volcanic rock on Earth's surface.
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Speleology is the scientific study of what?
Caves
Speleology examines how caves form, how water moves through them and what lives inside, drawing on geology, hydrology and biology. It comes from the Greek spelaion, meaning cave. Exploring caves purely as a sport is called caving or potholing instead.
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Rainwater slowly eats limestone away until caves open underground. Which kind of weathering is that?
Chemical weathering
Acidic groundwater chemically breaks down limestone, so this is chemical weathering.
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Which rock forms from buried plant material squeezed by heat and pressure?
Coal
Coal begins as peat from swamp plants, which heat and burial slowly compress into rock.
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What process commonly builds a coastal spit?
Longshore drift
Longshore drift moves sediment along the coast, allowing it to accumulate into a narrow ridge called a spit. Spits often develop where the shoreline changes direction or crosses a river mouth.
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What landform develops where a stream exits a steep mountain canyon?
Alluvial fan
An alluvial fan forms when a stream leaves a steep canyon, slows down on flatter ground, and spreads out sediment in a fan-shaped deposit. The coarsest material is usually deposited nearest the canyon mouth.
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What Earth layer is broken into the plates of plate tectonics?
The lithosphere
The lithosphere is Earth's rigid outer shell, the crust plus the uppermost slice of the mantle, typically around a hundred kilometres thick. It is cracked into the tectonic plates that drift, collide and grind past one another, raising mountains and setting off earthquakes.
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Which Earth layer is liquid and helps generate the magnetic field?
Outer core
Convection of molten iron alloy in the outer core powers the geodynamo.
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Which principle says undisturbed younger sedimentary layers lie above older ones?
Superposition
Superposition provides relative ages in layered rocks.
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What combination makes a fossil especially useful for correlating rock layers?
Short time range and wide distribution
Index fossils identify a narrow interval across broad areas.
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What fossilized tree resin, often golden and translucent, sometimes preserves insects trapped inside it?
Amber
Amber is tree resin that has hardened and set over millions of years. Insects, spiders and occasionally a lizard or a feather caught in the fresh sticky flow can end up preserved inside in remarkable detail.
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What ridge of debris is deposited at or beside a glacier?
Moraine
A moraine is a ridge or mound of rock, soil, and other debris deposited by a glacier. Moraines can mark the glacier’s former edge and reveal how far it once advanced.
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What unsorted sediment is deposited directly by glacier ice?
Till
Glacial till contains a mix of clay, sand, gravel, and boulders.
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Which mineral is the form of carbon used in pencil ‘lead’?
Graphite
Graphite is carbon arranged in weakly bonded sheets that slide off onto paper. Diamond is the same element with a much harder structure.
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The Hawaiian island chain is commonly explained by what geological feature?
A mantle hotspot
Hawaii's island chain is commonly explained by the Pacific Plate moving over a relatively stationary mantle hotspot.
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A landscape of caves and sinkholes formed by dissolving limestone is called what?
Karst
Carbonic-acid groundwater dissolves soluble carbonate rock.
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Which mineral gives many metamorphic rocks a sparkling, flaky look?
Mica
Micas split into paper-thin sheets that catch the light, which is why schists glitter.
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What mineral is commonly known as rock salt?
Halite
Halite is sodium chloride, the same compound as table salt, grown into cubic crystals. It forms as an evaporite: a sea or lake dries out and leaves its dissolved salt behind, sometimes in buried beds hundreds of metres thick.
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What property is the color of a mineral's powdered mark?
Streak
A streak plate reveals the mineral's powder color.
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Which element makes up the largest share of Earth’s crust by mass?
Oxygen
Oxygen is close to half the crust by mass, because most rock-forming minerals are silicates built around oxygen atoms.
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What tectonic setting is linked to mountain building and deep-ocean trenches?
Convergent boundary
At a convergent boundary two plates move toward each other. Where two continents meet, neither will sink, so the crust crumples upward into ranges like the Himalayas. Where an ocean plate meets another plate it bends and dives beneath it, gouging out trenches such as the Mariana and feeding the arc of volcanoes behind them.
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Quartz is composed of which two elements?
Silicon and oxygen
Quartz is silicon dioxide, SiO2. Each silicon atom is bonded to oxygen in a rigid three-dimensional framework, which is what makes it hard enough to scratch glass. It is one of the most abundant minerals in the Earth's crust, and the main ingredient of granite, sandstone and most beach sand.
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Which mineral is the main source of the silica used to make ordinary glass?
Quartz
Ordinary glass is melted mostly from silica sand, which is made of grains of quartz.
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Where does a meandering river usually cut into its channel?
The outer bank
Flow is fastest along the outside of a meander, where it commonly erodes the bank.
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What S-wave behavior helped identify Earth's outer core?
They cannot travel through liquids
S-waves cannot travel through liquids, so their absence beyond certain distances helped show that Earth’s outer core is liquid. This creates an S-wave shadow zone on the far side of Earth after an earthquake.
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What is the record for the heaviest pumpkin ever grown?
2,819 lb (1,278.8 kg)
Twin brothers Ian and Stuart Paton grew a 1,278.8 kg pumpkin, nicknamed Muggle, presented at Wargrave in Berkshire in October 2025. It took the circumference record at the same time, measuring 649.8 cm around from stem to blossom.
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The "Welcome Stranger," found in Australia in 1869, is the largest alluvial gold nugget ever discovered. About how much did it weigh as found?
About 109 kg (241 lb)
Cornish miners John Deason and Richard Oates found it just 3 cm below the surface near Moliagul, Victoria. It was too big for any scale in town, so a blacksmith broke it into three pieces on an anvil before it could be weighed and sold to a local bank.
Hard Geology Trivia Questions
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What do geologists call an enormous mass of intrusive igneous rock that cooled deep underground?
A batholith
Batholiths cover hundreds of square kilometres once erosion strips the cover off them. The granite of Yosemite is part of one.
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What glacial landform is a smooth, streamlined hill built largely of till?
A drumlin
Drumlins are moulded under moving ice and point the way the glacier travelled, often appearing in whole fields of them.
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What is a boulder called when it is left stranded on bedrock of a completely different type, far from where it formed?
A glacial erratic
An erratic is made of rock that does not match the ground it sits on, which is how geologists traced the paths of vanished ice sheets.
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A buried shell slowly dissolves away and leaves an empty impression in the surrounding rock. What is that fossil called?
A mold
The empty cavity is the mold. If sediment or minerals later fill that cavity, the solid copy left behind is a cast.
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What is a fragment of foreign rock trapped inside an igneous rock called?
A xenolith
Rising magma tears off chunks of the rock it passes through and carries them up, so xenoliths are one of the few direct samples we get of the deep mantle.
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What is a slice of old ocean floor and upper mantle shoved up and exposed on dry land called?
An ophiolite
Ophiolites let geologists walk over oceanic crust without a submarine. The Troodos massif on Cyprus and the mountains of Oman are the classic examples.
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Aluminum is extracted mainly from which ore?
Bauxite
Bauxite is a tropical weathering product rich in aluminum hydroxides. Galena, sphalerite and chalcopyrite are ores of lead, zinc and copper.
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What coastal process concentrates energy on headlands and causes uneven erosion?
Wave refraction
Wave refraction bends waves as they enter shallow water, focusing their energy on headlands and spreading it through bays, so headlands erode faster. The wave fronts bend because the part in shallow water slows first.
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Yardangs are streamlined ridges carved mainly by what?
Wind erosion
Yardangs are cut by abrasion from wind-blown sand in arid regions, and they line up with the prevailing wind. Those in Iran's Lut Desert run for tens of kilometres and are easily picked out from orbit.
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Earth's rigid outer shell slides over which underlying layer?
The asthenosphere
The tectonic plates ride on the asthenosphere, a hot, weak band of the upper mantle that creeps and flows over long timescales instead of snapping. It is still solid rock, but soft enough to deform, and that slow give is what allows the plates to move at all.
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Which scale do seismologists now use to compare the size of large earthquakes?
Moment magnitude scale
The Richter scale saturates: above roughly magnitude 7 it stops telling big quakes apart. Moment magnitude, calculated from the area of the fault, how far it slipped and how rigid the rock is, does not, so it is what seismologists actually quote today, even when news reports still say 'on the Richter scale'.
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What process formed Giant’s Causeway’s basalt formations?
Columnar jointing
Giant’s Causeway formed through columnar jointing, as cooling basaltic lava contracted and cracked into its distinctive polygonal columns.
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Which fossilization process fills the tiny pore spaces of buried bone or wood with minerals?
Permineralization
Groundwater seeping through buried bone or wood carries dissolved minerals into its empty pores and leaves them behind as crystals. The original material stays where it is, which is why petrified wood can still show its growth rings and cell walls.
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A thin clay layer found worldwide marks the K-Pg boundary, where the dinosaurs died out. Which element is strangely abundant in it?
Iridium
The boundary clay holds iridium at up to a hundred times the level found in ordinary crust. Iridium is scarce on Earth's surface but common in asteroids, and in 1980 the Alvarez team used that anomaly to argue that an impact ended the Cretaceous. The Chicxulub crater off the Yucatan coast was identified as the site about a decade later.
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What is the name for a surface in a rock sequence where a long span of geologic time is simply missing?
An unconformity
An unconformity is a buried gap. Rock was laid down, then lifted and worn away, or no sediment arrived for a long stretch, before deposition resumed on top. Hutton's Siccar Point in Scotland exposes one where tilted greywacke meets flat red sandstone with roughly 65 million years absent in between.
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A sharp pyramidal peak carved by several cirques is a glacial what?
Horn
Headward erosion by multiple cirques can leave a horn such as the Matterhorn.
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Which geologist first articulated that everyday geologic processes shape Earth over deep time?
James Hutton
James Hutton argued that the same slow processes we observe today, such as erosion, wave action, and sediment transport, shaped Earth over immense spans of time. This idea became known as uniformitarianism, often summarized as “the present is the key to the past.”
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Who popularized uniformitarian geology through Principles of Geology?
Charles Lyell
Charles Lyell popularized uniformitarian geology through his multivolume Principles of Geology, arguing that the same gradual processes seen today shaped Earth’s past. His ideas strongly influenced Charles Darwin’s thinking about gradual change.
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Who produced an early nationwide geologic map of England?
William Smith
Smith published a landmark geologic map of England in 1815, helping establish systematic stratigraphic mapping.
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What term describes a fossil deposit holding an exceptional number of unusually well preserved organisms?
Lagerstätte
German for a storage place, a Lagerstätte can preserve soft tissue as well as bone and shell. The Burgess Shale is the famous example.
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What is a lahar?
A volcanic mudflow
Water mixed with volcanic ash and debris can rush downslope as a lahar.
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Which seafloor pattern provided the key evidence for seafloor spreading?
Symmetric magnetic stripes
New crust forming at a mid-ocean ridge locks in the direction of Earth's magnetic field as it cools. Because the field flips polarity every so often, the crust records alternating bands of normal and reversed magnetism. Those bands appear as matching mirror images on both sides of the ridge, which only makes sense if the seafloor is spreading outwards from it.
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Lodestone, the rock used in the earliest compasses, is made mostly of which mineral?
Magnetite
Lodestone is magnetite, an iron oxide, that has been magnetized in nature. A suspended piece settles pointing north–south.
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What texture shows minerals aligned in layers within many metamorphic rocks?
Foliation
Foliation is a layered or banded texture produced when pressure aligns minerals during metamorphism.
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What depositional feature commonly forms along the inside of a meander bend?
Point bar
A point bar forms where sediment accumulates along the inside of a meandering river bend.
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Which process turns loose sediment into solid sedimentary rock?
Lithification
Lithification is the hardening of loose sediment into rock: burial squeezes the grains together and minerals carried by groundwater cement them in place. Weathering and erosion run the other way, breaking existing rock down into the sediment in the first place.
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Quartzite forms when heat and pressure alter which sedimentary rock?
Sandstone
The quartz grains of sandstone fuse together into quartzite. Limestone would instead become marble, and shale would become slate.
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What name is given to the suspected episodes when ice may have covered almost the entire surface of the planet?
Snowball Earth
Snowball Earth describes deep freezes, mostly around 700 million years ago, when glacial deposits turn up even in rocks that formed near the equator.
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Around 540 million years ago most major animal groups appear in the fossil record within a geologically short span. What is that event called?
The Cambrian explosion
Nearly every animal body plan alive today shows up in early Cambrian rocks, in a burst lasting a few tens of millions of years.
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Which boundary separates Earth’s crust from the mantle below it?
The Mohorovičić discontinuity
Usually shortened to the Moho, it was spotted in 1909 as a sudden jump in the speed of earthquake waves. The Gutenberg discontinuity is the core–mantle boundary instead.
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What is the collective name for fragments ejected during a volcanic eruption?
Tephra
Tephra includes ash, lapilli, and volcanic bombs.
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Crystals from Australia’s Jack Hills, dated to about 4.4 billion years old, are the oldest known fragments of Earth’s crust. Which mineral are they?
Zircon
Zircon is tough enough to survive being eroded and recycled, and it traps uranium that acts as a built-in clock.
Answered in full
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- Quartz is composed of which two elements?
- Which process turns loose sediment into solid sedimentary rock?
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