Earth Science questions

75 fact-checked questions — tap any to predict the answer, then read why.

• Why can a river turn orange downstream even if the strongest acidic water enters from one tiny spring along the bank?
• Why might two Arctic streams look similarly rusty but need different chemical diagnoses?
• Why can thawing permafrost make a stream more acidic instead of simply adding cold meltwater?
• In the folded Appalachians, why can one rock layer stand as a ridge while the layer beside it becomes a valley?
• Why do some fresh earthquake fault scarps become rounded faster than others?
• Why can a long active fault affect more river basins than a short one?
• Why can rocks near active faults erode faster than heavy rainfall alone would suggest?
• If cosmic rays slowly build up beryllium-10 inside quartz grains, but only while those grains sit in roughly the top metre of soil and rock, why does river sand that carries very little beryllium-10 tell geologists that the whole basin upstream is eroding quickly?
• Earthquake shaking lasts only seconds, so how can it leave rock easier for later rivers to erode?
• Why do rivers near active faults erode faster than rivers farther away?
• If two river basins get similar rain and have similar rock, why might the one closer to active faults erode faster?
• Why can eruptions that form a large igneous province, a huge region of volcanic rock, harm marine life far from the lava?
• Why do CO2 and SO2 from large eruptions affect climate differently?
• Sills are buried magma sheets. Why can Siberian sills pose more risk than lava?
• What does the chain of Hawaiian volcanoes record as it gets older toward the northwest?
• Why can a broad, hot mantle plume head produce a huge basalt province?
• How can a mantle plume, which is hot solid rock rather than a lava pipe, make magma?
• Why are deep-sea mid-ocean ridges, Earth's longest mountain system, so volcanic even though they lie underwater?
• After the asteroid impact that ended the dinosaurs, what did ocean recovery lean on before normal food webs returned?
• Why might larger diatoms outlive smaller chalky nannoplankton in K-Pg seas?
• K-Pg shelled plankton died off in days. Why does darkness explain it better than acid dissolving shells?
• After an asteroid impact darkens the whole planet, why might tropical plankton die off more than polar plankton?
• Why did the smallest plankton survive best after the K-Pg impact darkened the oceans?
• What drives the mid-ocean ridges that erupt more lava every year than all land volcanoes combined?
• On the deep seafloor, why do gas bubbles in lava stay small while surface lava bursts into ash?
• How can melting ice make Icelandic volcanism spike instead of calm down?
• What helped Surtsey survive storms while nearby Surtseyan islets vanished?
• Why can broad ash deposits around a submarine volcano suggest that some vents reached the sea surface?
• Why can shallow underwater volcanic cones end up with flat tops at nearly the same depth?
• Why can a shallow Reykjanes seafloor volcano blast harder than a deep one?
• Why do deep mid-ocean ridges usually ooze lava instead of blasting ash?
• What is Earth's inner core roughly as hot as?
• What actually moves Earth's magnetic north pole?
• What helps replace the phosphorus that heavy rain washes out of the Amazon's thin soil each year?
• Why did the Kola Superdeep Borehole project stop after reaching about 12 km?
• What keeps pushing India northward into Asia, tens of millions of years after the two collided?
• Why do deserts get cold at night?
• Why do mountains have tree lines?
• Why do some beaches have black sand?
• Why does quicksand trap people?
• Why does sandstone have layers?
• Why are fossils usually flat?
• Why do tides happen twice daily?
• Why do some islands sink?
• Why do opals show rainbow colors?
• Why are icebergs freshwater not salty?
• Why do some rocks glow under a UV lamp?
• Why do rivers meander in curves?
• Why do cliffs erode into arches?
• Why do fossils form in sedimentary rock?
• Why can solid-looking ground suddenly collapse in a limestone area?
• Why do minerals form crystals?
• Why are some deserts, like the Namib in Africa, found right next to the ocean?
• How do valleys form in mountains?
• Why are some rocks magnetic?
• Why do hot springs exist?
• Why does Earth have magnetic poles?
• Why do sand dunes move?
• Why do caves have stalactites?
• Why do geysers erupt regularly?
• Why does magma eventually burst out of a volcano instead of staying underground?
• Why do mountains have snow on top?
• Why do deserts exist?
• Why is underground water cold?
• Which process can build up new land above the sea surface?
• Why do we usually find fossils embedded in solid rock?
• Why are there waves in the ocean?
• How are caves formed?
• Why do glaciers move?
• How does rock become sand on a beach?
• Why do rivers flow to the ocean?
• Why does earth have different layers?
• Why do tsunamis happen?
• Why do earthquakes happen?
• Why is the ocean salty?