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Scientists examine the pits using 1-meter-by-1-meter grids
STANDARDS
CCSS: 7.SP.B.3, MP2, MP3
TEKS: 6.12B, 6.13B, 7.12A
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Stuck in the Pits
A treasure trove of fossils lies in the heart of Los Angeles
About 40,000 years ago, Los Angeles, California, was teeming with exotic wildlife. Mammoths, saber-toothed cats, giant sloths, and camels roamed the region. Dinosaurs were long gone, and huge mammals ruled the land.
Today, scientists are piecing together the city’s wild past from fossils found in the La Brea Tar Pits. Located in downtown Los Angeles, it’s one of the world’s most famous fossil excavation sites.
The soil under the city is filled with oil deposits that formed naturally over millions of years. Eventually the pressure caused by the weight of the rocks above forced some of the oil to rise to the surface, creating oily tar pools. The sticky pools trapped unlucky animals passing by. The black, gooey asphalt preserved everything from massive mastodons to tiny mice. Even insects, plants, and twigs have been found in the ancient sludge.
In 1875, the first fossil was discovered: the long, curved tooth of a saber-toothed cat. Since then, paleontologists have found about 3.5 million fossils belonging to more than 600 animal and plant species in the tar.
After the fossils have been removed, they clean and sort the bones in the lab
At the La Brea Tar Pits and Museum, visitors can watch scientists dig up fossils every day. Visitors will see—and smell—large, muddy-looking pools of tar and water around the park. Many of the pools where paleontologists have already excavated all the fossils have been fenced off. But new sticky seeps appear all the time, so visitors must be careful where they step!
“You’ll be walking around the park and see yellow cones with tar spattered on them, warning people not to walk there,” says Emily Lindsey, a curator at the museum. “Things still get trapped in them. Bugs, squirrels, and even trash. It’s a modern-day record of life.”
A statue of a mastodon trapped in tar at the La Brea Tar Pits and Museum in downtown Los Angeles.
Whenever construction happens in nearby office buildings or shops, there’s a good chance more tar pits will be uncovered—and more fossils. Last November, construction workers building a new train stop unearthed a skull and tusks from an ancient mammoth or mastodon.
“Construction just started on another Metro station right across the street from the museum,” says Lindsey. “It’s likely that workers will not only find fossils, but potentially whole new tar pits containing tens of thousands of fossils.” Each fossil will help reveal what life was like back when these creatures ruled the Earth.
Scientists collect data about the different species of animals they find in the tar pits and when the animals lived. A double-bar graph allows you to compare two data sets in the same graph. You can use it to determine trends in the data.
The graph above shows the number of mammal and bird species found in the La Brea Tar Pits from two different periods of time called epochs. The number of different species found in the pits provides a snapshot of what life was like during each epoch.
What two data sets are being compared in this double-bar graph?
From which epoch did scientists dig up more large mammal species?
Did scientists find more large or small bird species from the Pleistocene epoch?
Which type of animal had the greatest difference between the number of animal species found in the Pleistocene and the Holocene?
What general comparison can you make between large and small categories of animal species (both mammals and birds) that were found in the tar pits in the Pleistocene and Holocene epochs? Explain your answer.