40 Fun Facts About Shale

Which famous waterfall keeps retreating upstream because soft shale crumbles away beneath a hard dolomite cap?

Niagara Falls pours over tough Lockport dolomite resting on softer Rochester shale. The river wears the shale away until the unsupported cap breaks off in great chunks.

Heat and pressure deep underground turn shale into which harder rock, long split into roofing tiles and blackboards?

Slate is what shale becomes when metamorphism hardens it. It still splits into smooth, flat sheets, which is why it also tops billiard tables.

Which South American country's giant shale oil and gas field is called Vaca Muerta, Spanish for dead cow?

Argentina's Vaca Muerta lies beneath the Neuquén Basin in northern Patagonia. The country completed its first shale gas well there in 2010.

Besides fossils and animal tracks, the flat bedding surfaces of shale sometimes preserve tiny craters left by what?

Raindrops that pitted soft mud long ago can survive as dimples once the mud hardens into shale. A single ancient shower can still be read on the rock, alongside burrows and footprints.

Black shales that split into extremely thin sheets are nicknamed after which everyday material?

Paper shales peel apart like the pages of a book. Oily molecules stick to the faces of the mineral flakes and weaken the bonds between them, so the rock separates very easily.

The Bright Angel Shale and the Hermit Shale are colorful rock layers exposed in the walls of which American landmark?

Grand Canyon walls include the greenish Bright Angel Shale, whose soft beds erode into gentle slopes rising from the Tonto Platform, far below the rim.

The word shale probably comes from an Old English term for which object, a hint at how the rock flakes apart?

Shell is the likely root: Old English scealu meant a husk or outer casing, a fitting image for a rock that peels away in thin flakes.

Which technique for freeing natural gas from shale was banned by France in 2011 and by Vermont in 2012?

Fracking pumps fluid into shale at high pressure to crack the rock so trapped gas can flow. France was the first nation to ban it, and Vermont the first US state.

Which fine material makes up more than half of a typical shale?

Clay minerals make up about 58 percent of a typical shale, in flakes far too small to see. Their flat shape is what lets the rock split into sheets.

Commercial quarries in Utah's Wheeler Shale dig up huge numbers of which extinct sea creatures for fossil collectors?

Trilobites of the species Elrathia kingii are so plentiful in the Wheeler Shale that one commercial collector estimated digging up 1.5 million of them in 20 years.

Shale gas, like the natural gas burned in kitchen stoves, consists mostly of which simple compound?

Methane makes up most of shale gas, as it does ordinary natural gas. The difference is where it hides: locked inside the shale itself instead of pooling in a porous reservoir.

Which 2010 documentary about shale drilling made headlines with a scene of a man setting his tap water alight?

Gasland follows director Josh Fox from Pennsylvania across the American West, meeting families who live beside gas wells. It was nominated for the Academy Award for Best Documentary Feature.

Which science writer made the Burgess Shale fossils famous with the 1989 bestseller Wonderful Life?

Stephen Jay Gould used the site's bizarre animals to argue that evolution turns on contingency, not steady progress. His book was a finalist for the Pulitzer Prize.

Which Burgess Shale animal, with five eyes and a clawed trunk, made scientists laugh when it was first presented?

Opabinia looked so strange that the audience laughed when Harry Whittington first presented his analysis. The clawed trunk most likely passed food to a mouth that faced backwards.

Black shale forms in stagnant water that lacks which dissolved gas, so buried plankton and plants never fully decay?

Oxygen was missing from the stagnant basins where black shales formed, so dead organic matter piled up instead of rotting. That buried material is what darkens the rock.

Black shales along the Atlantic Ocean's margins formed in stagnant basins as which supercontinent broke apart?

Pangaea's breakup opened a narrow young Atlantic with sluggish circulation. Its very warm Cretaceous seas lacked the cold bottom currents that stir the deep oceans today.

The world's two largest oil shale-fired power stations were built near the city of Narva, in which Baltic country?

Estonia has historically burned most of the oil shale it mines to generate electricity, treating the rock much as other countries treat coal.

James 'Paraffin' Young opened the world's first commercial oil works, sparking a shale oil boom in which country?

Scotland had about 120 shale oil works by 1865, and at its peak the industry supplied 2 percent of the world's oil. Young's first works opened at Bathgate in 1851.

Which country's Messel Pit, an old oil shale quarry that nearly became a landfill, is now a World Heritage fossil site?

Germany's Messel Pit preserves pygmy horses, bats and early primates in oil shale laid down on an ancient lake bed. Strong local resistance stopped the landfill plan.

Which term do geologists use for shale's defining habit of splitting into thin layers along its bedding?

Fissility comes from countless flat mineral flakes lying parallel to one another. Rocks made of the same fine mud but lacking that alignment do not peel into sheets at all.

Which hard mineral, the main ingredient of most beach sand, makes up roughly a quarter of a typical shale?

Quartz makes up about 28 percent of a typical shale, mostly as tiny grains that were washed in with the original mud.

Which iron oxide mineral gives red shales their color?

Hematite is iron in its oxidized, rust-like state. Where the iron has been chemically reduced instead, the same kind of rock shifts from reddish to greenish.

Which iron sulfide mineral often turns fossils in black shale into gleaming, brass-colored replicas?

Pyrite, better known as fool's gold, forms in stagnant seafloor mud and can take the place of a buried animal's remains, leaving a metallic copy.

Which process, driven by the weight of sediment piling up above, squeezes the water out of mud to form shale?

Compaction packs the mineral grains closer together and forces flat flakes into parallel layers. That alignment gives shale its sheet-like fabric.

Petroleum geologists give shale which name, because it is the place where oil and gas most commonly form?

Source rock is where oil and gas are born. Shale and its muddy relatives hold about 95 percent of the organic matter found in all sedimentary rocks.

Which solid organic material in oil shale, named from the Greek for wax, turns into oil only when the rock is heated?

Kerogen is oil that nature never finished cooking. Heat and pressure underground have not yet turned it into petroleum, so people must heat the shale to do the job.

Which gas-rich black shale, stretching beneath much of Pennsylvania and West Virginia, takes its name from a village?

Marcellus gave its name to the formation in 1839, thanks to a distinctive outcrop of black shale near the village. The rock itself extends through much of the Appalachian Basin.

The Barnett Shale, where modern shale gas drilling was pioneered, lies directly beneath which Texas city?

Fort Worth sits right on top of the field. Much of the gas lies beneath the city itself, which has complicated drilling in a fast-growing urban area.

Which Texas businessman is credited with pioneering shale gas after years of stubborn experiments in the Barnett Shale?

George Mitchell kept drilling the Barnett through years of weak wells and low gas prices until his methods paid off. He also developed The Woodlands, a planned community north of Houston.

The oil-rich Bakken Formation, a shale layer deep beneath the Williston Basin, is named after a man of which occupation?

Farmer Henry Bakken owned the land near Tioga where drillers first discovered the formation, so the rock took his family name.

The Green River Formation, the world's largest oil shale deposit, spans parts of Utah, Wyoming and which other state?

Colorado shares the deposit, which formed on the floors of ancient mountain lakes. The same lake beds are famous for exceptionally well-preserved fossil fish.

America's first natural gas well, dug by hand into shale in the village of Fredonia, was in which state?

New York's Fredonia had gas lights in two stores, two shops and a mill by 1825, fed through a pipeline of hollowed-out logs sealed with tar and rags.

Crushed shale is mixed with water, molded and fired in kilns to make which common building material?

Bricks are fired from shale or similar fine earth, and the mineral mix sets the color: a high iron content gives pink bricks, while more lime gives white or yellow ones.

Which Smithsonian Institution chief discovered the Burgess Shale fossils in 1909 and dug there for years afterward?

Charles Walcott returned to his quarry almost every year until 1924. Describing the fossils became a vast undertaking that he pursued until he died in 1927.

The Burgess Shale animals lived in which geological period, famous for an explosion of new life forms?

Cambrian fossils usually keep only hard parts, but the Burgess Shale is one of the earliest fossil beds to preserve imprints of soft tissue as well.

Holzmaden's Posidonia Shale is famous for fossils of which dolphin-shaped sea reptiles, some carrying unborn young?

Ichthyosaurs from Holzmaden are preserved so finely that dark outlines trace the whole body, giving the first evidence that the animals had a dorsal fin.

Which extinct animal, the state fossil of Illinois, is known only from the Francis Creek Shale at Mazon Creek?

Tully monster fossils show a cigar-shaped body, eyes on stalks and a long snout tipped with teeth. Scientists still debate whether the animal had a backbone.

Which term covers the physical and chemical changes that slowly turn buried mud into solid rock such as shale?

Diagenesis starts only a few tens of meters down, where burrowing animals still churn the mud, and continues as deeper burial squeezes and cements the grains.

The fine mud that becomes shale, slow to sink through water, usually builds up in which kind of place?

Quiet lake floors, lagoons, river deltas and deep offshore seabeds all let fine particles settle. The flecks that make shale stay suspended long after heavier sand has dropped out.

Some black shales are unusually rich in which radioactive heavy metal, alongside molybdenum, vanadium and zinc?

Uranium and other heavy metals are enriched in some black shales. Geologists still dispute whether hot fluids delivered them or whether they slowly settled out of seawater.