Level 1 — Absolute Beginner
Scientists use a new way to find out how old a place is. The place is the Mammoth Site in South Dakota, in the United States.
More than 60 mammoths are in this place. A mammoth is a huge animal with long tusks. It looks like a big, hairy elephant. The animals fell into a deep hole called a sinkhole and could not get out.
People thought the bones were about 26,000 years old. Now a new test says they are much older. The mammoths lived between 160,000 and 232,000 years ago.
The test uses light. It checks when the sand around the bones last saw the sun.
- mammoth
- A huge ancient animal like an elephant with long tusks.
- tusk
- A long, pointed tooth that sticks out of an animal's mouth.
- sinkhole
- A deep hole in the ground.
- bones
- The hard white parts inside an animal's body.
- test
- A way to find out something.
- sand
- Tiny pieces of rock, like on a beach.
- ancient
- Very, very old.
- scientist
- A person who studies the world.
Level 2 — Elementary
A famous fossil site in South Dakota is much older than people thought. New research says the mammoths at The Mammoth Site in Hot Springs lived between 160,000 and 232,000 years ago. Before this, the accepted age was only about 26,000 years.
Since 1974, scientists have found more than 60 mammoths there, mostly young males. This is the largest group of mammoths in North America. The animals fell into a sinkhole, which was a trap with steep sides.
The new age comes from a method called luminescence dating. It measures the last time grains of sand were exposed to sunlight. After the sand is buried in the dark, it slowly stores energy, and scientists can measure it to tell how long it has been hidden.
The study was published in the journal Quaternary Research on August 11, 2026. Shannon Mahan of the United States Geological Survey and Jim Mead, who is a researcher at the site, led it. The result moves the mammoths back by more than 100,000 years.
- fossil
- The remains of a plant or animal from long ago, kept in rock.
- accepted
- Agreed to by most people.
- trap
- Something that catches an animal or person.
- steep
- Rising or falling very sharply.
- luminescence dating
- A way to find age by measuring stored energy in grains of sand.
- exposed
- Open to something, like light.
- buried
- Covered by earth or sand.
- researcher
- A person who studies a subject carefully.
Level 3 — Intermediate
A new study has pushed back the age of The Mammoth Site in Hot Springs, South Dakota, by more than 100,000 years. Using luminescence dating, researchers conclude that the sinkhole's mammoths died between 160,000 and 232,000 years ago, far earlier than the roughly 26,000 years that had been widely accepted.
The site, discovered in 1974, holds more than 60 mostly young male Columbian mammoths, the largest concentration of the animals in North America. They are thought to have stumbled into a sinkhole with slippery walls from which they could not climb out, creating what scientists call a time capsule of the Ice Age.
Luminescence dating works by measuring energy that mineral grains accumulate while buried. When sediment is exposed to sunlight, that stored signal resets; once it is hidden underground, the signal builds again at a steady rate. By measuring how much has built up since burial, scientists can estimate when the sediment was last exposed.
The paper, published in Quaternary Research on August 11, 2026, was led by Shannon Mahan of the United States Geological Survey and Jim Mead, an emeritus researcher at the site, with colleagues including Chris Jass. The new dates place the mammoths in a much earlier chapter of the Ice Age, which may change how researchers connect the fossils to ancient climate.
- concentration
- A large number of things in one place.
- Columbian mammoth
- A large Ice Age mammoth species that lived in North America.
- time capsule
- Something that preserves a moment from the past.
- accumulate
- To gather or build up over time.
- sediment
- Sand, mud or small pieces of rock laid down by water or wind.
- emeritus
- Retired but keeping an honorary title.
- signal
- Information that can be measured.
- estimate
- To judge roughly how much or how old something is.
Level 4 — Advanced
The Mammoth Site in Hot Springs, South Dakota, is substantially older than long assumed, according to a luminescence dating study that places the death of its mammoths between 160,000 and 232,000 years ago, more than 100,000 years before the roughly 26,000 year estimate that had prevailed. The paper appeared in Quaternary Research on August 11, 2026.
Since its discovery in 1974, the sinkhole has yielded more than 60 predominantly young male Columbian mammoths, the densest assemblage of the species in North America. The skewed demographic is generally attributed to the animals blundering into a steep sided pit that offered no escape, a natural trap that preserved its victims for millennia.
Luminescence dating exploits a quirk of mineral physics: grains accumulate trapped electrons from natural radiation while buried, and exposure to sunlight resets that charge to zero. Measuring the accumulated signal in the sediment, and dividing by the rate at which it builds, yields the time elapsed since the grains were last illuminated.
The study was led by Shannon Mahan of the United States Geological Survey and Jim Mead, an emeritus researcher at the site, with Paul Hanson, Emma Krolczyk and Chris Jass. By moving the assemblage into a far earlier chapter of the Ice Age, the revised chronology compels scientists to reassess the climate and ecology against which these animals lived and died.
- prevailed
- Remained the most widely accepted view.
- assemblage
- A group of fossils found together.
- skewed
- Unevenly distributed, leaning to one side.
- demographic
- The make up of a population, such as age and sex.
- millennia
- Thousands of years.
- exploits
- Makes clever use of.
- revised
- Changed after new information.
- chronology
- The order and dating of past events.
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