JumpStart - Earth Science
Amber - Window To The Past*

Air bubbles, amber, and dinosaurs

Ages of ice samples found on the Earth cover a span approaching 200,000 years. But how can we tell what the Earth s atmosphere was like before that? Recently, USGS scientists have used a gas QMS to determine the oxygen level of ancient samples of Earth s atmosphere from a most unlikely place amber. The fossilized resin of conifer trees, amber is interesting to scientists as a medium that traps insects, small animals, and plants, preserving them through geologic time for future study.

This 84-million-year-old air bubble lies trapped in amber (fossilized tree sap). Using a quadrupole mass spectrometer, scientists can learn what the atmosphere was like when the dinosaurs roamed the earth.

The consequences of an elevated oxygen level during Cretaceous time are speculative. Did the higher oxygen support the now extinct dinosaurs? Their demise was gradual in the transition from late Cretaceous to early Tertiary times, as was the decrease in oxygen content of the atmosphere.

This chart shows a major decrease in oxygen content in the atmosphere from 35 percent to the present day level of 21 percent. This decrease occured about the same time that the dinosaurs disappeared--65 million years ago.

Amber is an Organic Gemstone

Amber is highly prized for its beauty and rarity. However, it is not as durable as gemstones from minerals:

Amber (hardness: 2-2.5 Mohs)
A mixture of hydrocarbons
Specific gravity: 1.05-1.096

Hard fossil resin or sap of ancient pine trees. Usually amorphous (lacks crystalline structure). Sometimes mined, sometimes gathered on seashores.

Varies from transparent to semitransparent and generally from light yellow to dark brown, but can be orange, red, whitish, greenish-brown, blue, or violet. Can be dyed in any color.

Takes a fine polish. Used mainly in making beads or other ornaments.