La Brea Tar Pits and Museum

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La Brea Tar Pits and Museum
La Brea Tar Pits
Did you know you are standing above a large underground oil
field? This oil seeps to the surface as sticky asphalt. Plants and
unwary animals have been getting trapped in this treacherous
goo for thousands of years. Being stuck in the La Brea Tar Pits
was a terrible way to die – but a great way to preserve fossils!
What’s really in the Tar Pits?
For centuries, people have called these the La Brea Tar Pits.
But the black goo you see here is actually asphalt, the heavy
component of crude oil. Asphalt occurs naturally. Technically,
tar is something different, and it does not occur naturally.
Methane (natural gas) produces the bubbles you see in the Tar
Pits.
Lake Pit
The lake fills a quarry where asphalt was mined during the
nineteenth century. After the quarry was abandoned, rain and
groundwater seepage soon filled the excavated areas.
The surface oil slicks are composed of asphalt. This and the
bubbles of natural gas (methane) escape from fissures below
the lake.
Life-sized fiberglass models of a Columbian mammoth family
stand at the east end of the lake. The mother has become
trapped; her mate and offspring watch helplessly. There is a
life-sized model of an American mastodon near the west end
of the lake.
Pleistocene Garden
This Garden gives us a glimpse of California’s past 25,000 years
ago. The plants you see here represent several plant
communities that once grew in the Los Angeles Basin. Some of
these plants can still be found in the nearby mountains,
streams, and coastal bluffs.
Coastal sage scrub plants, like those recovered from the Tar
Pits, were found throughout the prehistoric L.A. Basin. These
plants suggest that the Late Pleistocene climate was wetter
and cooler than it is today.
Large grazing animals from the Pleistocene – mammoths,
bison, camels, and horses – roamed Ice Age L.A., feeding upon
the soft-leaved coastal scrub plants. These animals attracted
large carnivores like dire wolves, giant jaguars, and sabertoothed cats.
While so many large animals from the Pleistocene died out,
these plants managed to survive, as did every single plant
species we find preserved in the Tar Pits. Why is that? And
which ones will be here 25,000 years from now?
Pits 3, 4, 61 and 67
This enclosure contains four excavations. Pits 3 and 4, at the
east end of the enclosure, were over 30 feet in diameter and
extended to depths of more than 25 feet. Pit 3 yielded over
5000 fossil mammal skulls and a California juniper tree that has
been dated at 14,000 years old. More than 1,000 fossil birds
were obtained from Pit 4 together with other fossils dated
between 15,000 to 35,000 years old.
The fossils from Pits 61 and 67 on the west side of the
enclosure are about 12,000 years old. Dire wolves and sabertoothed cats were the commonest fossils from Pit 61, but
lions, deer, horses and ground sloths were also recovered.
More than 270 skulls were recovered from Pit 67, which is
noteworthy for the remains of bison, browsing ground sloths,
and young camels.
These four excavations were conducted by the Natural History
Museum of Los Angeles County from July 16, 1913, to June 21,
1915.
Pit 91: Active Fossil Dig
We first dug into Pit 91 in 1915 and continue to excavate here
in the summer. We’ve found fossils of extinct saber-toothed
cats and other large animals. We’ve also found fossils of
smaller animals and plants. Come inside and take a look!
How old?
The oldest fossils from Pit 91 date back 44,000 years. The most
recent fossils are 14,000 years old.
How deep?
We’ve dug 15 feet deep. We might find fossils up to five feet
deeper.
Did you know?
We’ve even found the fossils of flies that fed on dead animals
trapped in the Tar Pits.
Observation Pit
The Observation Pit opened in 1952 and was the Park’s first
Museum.
Finding fossils in asphalt takes hard work, and we have to dig
below the surface to locate them. This is one of the more than
a hundred pits that we dug looking for fossils in the park. Come
inside to see how fossils of an extinct mastodon, Harlan’s
ground sloth, and saber-toothed cat look when they are first
discovered by scientists!
Jumbled bones
Just because we find a saber-toothed cat with a horse leg
between its teeth, it doesn’t mean the big cat’s last meal was
western horse. Asphalt is sticky, especially when the weather is
warm, and liquid asphalt constantly seeps up from
underground. Over time – a long time – fossils move and
accumulate in a think mass of asphalt.
Project 23
In 2006, the Los Angeles County Museum of Art (LACMA)
began work on a new underground parking garage. During the
course of construction, 16 new fossil deposits were discovered,
including the semi-articulated, largely complete skeleton of an
adult mammoth (who we’ve nicked named Zed). How could we
get out of the way of bulldozers but save the fossils? We built
large wooden boxes around each deposit, 23 in all. The boxes
were moved to this location, and excavation began on “Project
23.” In addition to the boxes, there were 327 buckets of fossil
material recovered from the LACMA salvage site for
paleontologists to clean and sort through. It’s going to keep us
busy for years! At this active excavation site, scientists are
discovering new Ice Age fossils every day.
Big bones raise big questions
The Tar Pits trapped large animals that lived in the L.A. basin
from 55,000 to 11,000 years ago. Many of these species are
now extinct. Each fossil we find provides clues about life in L.A.
in the prehistoric past. But one of the biggest mysteries still
remains: Why did so many of the largest animals we find here
die out?
Tiny fossils give us clues
Tiny fossils of plants, insects and other small animals give us
information that we can’t get from large fossils. These
microfossils tell us about L.A.’s climate and habitat and how
they changed over the past 50,000 years. They can also help us
understand changes that are happening now – and may
happen in the future.
We invite you to visit the Museum to learn the exciting story of
the La Brea discoveries and view some of the many fossils we
have found right here in the Tar Pits.

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