Book 12, Question 91
Why Do Minerals Color Rocks Red or Yellow Near Vents?
Rocks near hot vents can turn red or yellow! Heat and water change the minerals in the rock. Geologists use those colors as clues.
More fun facts
- At Sulphur Banks on Kilauea volcano in Hawaii, two gases, sulfur dioxide and hydrogen sulfide, react to make pure yellow sulfur.
- Hawaiians call that yellow sulfur kukaepele, which means the waste of Pele.
- Sulfur dioxide smells like a struck match, while hydrogen sulfide smells like rotten eggs.
- Other sulfur gases make sulfuric acid, which breaks lava down into clay stained red and brown by iron oxide, a lot like rust.
- When hot water vapor and acidic gases cook rock and change its minerals, scientists call it hydrothermal alteration, from Greek words for water and heat.
- Shallow cracks give off only steam, while deep cracks that reach down toward magma let out volcanic gases that build sulfur deposits.
- In 1922, scientists drilled two holes at Sulphur Banks and found the temperature stayed at 96 degrees Celsius all the way down to 15 meters.
- Yellowstone's mudpots come in white, tan, pink, brown, grey and black, and their mud can contain pyrite, also called fool's gold.
Sources: National Park Service, National Park Service, U.S. Geological Survey
Questions kids ask
Is it safe to breathe near colorful vents?
Volcanic gases can be harmful, so park rangers advise people with asthma or heart problems, pregnant women, infants and young children to avoid the Sulphur Banks walk.
Is it spelled sulphur or sulfur?
Both are right. Sulphur Banks uses the British spelling chosen by visitors in the early 1800s, and sulfur is the American spelling.