Field Trip 12: The La Brea Tar Pits and Museum

Introduction

The La Brea Tar Pits contains the most complete record of fossils from the latest Pleistocene Period, the last part of the Ice Age. Fossils have been formally collected since 1905, yielding over a million bones, representing 231 vertebrates, and another two million fossils from plants and invertebrates. Excavations for fossil collecting and preparation of specimens are ongoing and can be observed during a visit to the tar pits and Page Museum.    

The Los Angeles region has produced over nine billion barrels of oil, this according to the American Oil and Gas Historical Society. These oil reserves are the source of the relatively rare asphalt seeps that are the pools of “tar” at the La Brea Tar Pits, in Hancock Park. Asphalt, also called bitumen, pitch, or tar, is a highly viscous, semi solid form of petroleum that can be used as a waterproofing sealant. In the 19th century, the La Brea Tar Pits were part of Rancho La Brea, where asphalt was being collected for commercial use for sealing leaking roofs and boats. In 1875, a fossilized canine tooth from a Saber-toothed cat was discovered. This was the first bone recognized as being from extinct fauna and the historic and scientific significance of this area was realized.

Three to four hours should be allotted to complete this field trip. This itinerary could also be combined with the field trip to the Natural History Museum, covered in the previous chapter. Parking is available on the premises for the La Brea Tar Pits and LACMA for $15 (at the time of this writing). Metered street parking may also be available. For pre field resources, including making reservations for your group, examine the La Brea Tar Pits website: resources for teachers. Links to an external site. Additional information may be obtained by calling (213) 763-3529.

Learning Objectives

Through participation in this field trip students should be able to:

  1. Recognize the paleontological significance of the La Brea Tar Pits
  2. Describe how and why so many fossils have been collected from the La Brea Tar Pits
  3. Compare and contrast the ecology of Los Angeles today to the ecology during the “late Pleistocene”/“late Ice Age”
  4. Describe the process of radiometric dating using the carbon-14 method

Key Vocabulary

Asphalt – highly viscous form of petroleum used as waterproof sealant and binding agent for roadways

Fossil – the preserved remains, impression, or trace of a past living organism

Microfossils – fossils that are very small in size, generally less than 1 mm

Pleistocene – an Epoch of geologic time, beginning about 2.6 million years ago and ending 10,000 years ago, during which time Earth has been in an Ice Age

Pre Field Trip Questions

Access the La Brea Tar Pits web page Links to an external site. for the information needed to answer the following questions:

  1. How long ago was the “late Pleistocene”?
  2. Describe the concentration of wildlife in Los Angeles during the late Pleistocene compared to today.
  3. Were mastodons and mammoths the same animal? If not, how were they different?
  4. Which Late Pleistocene mammal is most common in the fossil record of the La Brea Tar Pits?
  5. True or false, camels evolved in Africa then migrated to North America?

Page Museum Questions

A. (area A on map). The La Brea Tar Pits contain the most complete record of fossils from the “late Ice Age” (Late Pleistocene). This time frame spans: ___ to___ years ago.

Map of Page Museum.

Simplified map of the interior of the Page Museum.  Letters correspond to the locations of the answers to the lettered questions.  Not to scale.  

B. Why did animals get trapped in the tar?

  • Why would nocturnal animals be less likely to be trapped in the asphalt?
  • What does the presence of mollusks tell us about the past position of sea level in the La Brea Tar Pits area of Los Angeles?
  • Compare and contrast Mastodons to Mammoths.

C. Why are there so many Dire Wolf Skulls in the collection?

  • What microfossils are being studied?

D. Radiocarbon Dating Questions:

  • Carbon 14 (14C) starts off as which element?
  • What happens to this element to convert it to 14C?
  • How does 14C get into plants and animals?
  • How long is the half-life of 14C?
  • What does 14C change into as it decays?
  • Explain how the percentage of decay of 14C is used to determine how long ago an organism died?

“The La Brea Tar Pits have a remarkable collection of dinosaur fossils!” How would you correct this false statement? 

La Brea Tar Pits Questions (outside of the Page Museum)

Map of the La Brea Tar Pits.

Simplified map of the La Brea Tar Pits.  Numbers correspond to location of answers to numbered questions.  Not to scale. 

  1. Summarize the origin of the Lake Pit. Explain the origin of the tar.
  2. How does the tar help preserve bones as fossils?
  3. Explain why the name, “La Brea Tar Pits” is technically incorrect.
    • Where does asphalt come from?
    • Why does asphalt bubble?
    • Why would it be more likely for animals to be trapped during the summer than the winter or day vs. night?

Post Field Trip Assignment. Choose one of the questions below then prepare a one-page response.

  1. Using information gathered during this field trip, your course textbook, or information from other sources, such as open source textbooks Links to an external site. summarize the process a scientist would follow in order to obtain a radiocarbon date from a fossilized bone.
  2. Describe how the fossil record gathered from the La Brea Tar Pits indicates that the climate was different in Los Angeles during the late Pleistocene compared to today.
  3. Why have so many fossils been collected from the La Brea Tar Pits, especially considering that the animals were buried in asphalt?