Measuring ancient mountains

Dr. herb Meyer in front of Florissant's "The Big Stump"
Herb Meyer became the first permanent paleontologist for Florissant Fossil Beds National Monument in 1994. He is the author of The Fossils of Florissant. 




"I started collecting fossil plants in Oregon and wrote my first published paper while I was in high school, and that inspired me to become a paleontologist"
Dr. Herb Meyer

 

Measuring Ancient Mountains

Late Eocene fossil forests from the Pacific coast show the climate there was very warm and nearly tropical, while it was cooler and temperate here at Florissant.
If these ecosystems were situated at approximately the same latitude (40º North) at that time, why were they so different? Dr. Meyer was determined to find out.

Is Elevation the Answer?

The differences in temperature between coastal forests and here at Florissant could be partially explained by elevation.

But how can this hypothesis be tested?
Temperature decreases as elevation increases. Anyone who has traveled between Florissant and Colorado Springs has probably noticed similar changes in temperature over a relatively short distance.

The rate of this change can be measured and is known as a lapse rate.

Comparing the Eocene temperatures at sea level with those at Florissant would provide the answers Dr. Meyer was looking for.

 
Artists rendition of Late Eocene Pacific Coast Near-tropical Forest and Late Eocene Florissant Warm Temperate Forest
 

How High? How Cool?

What was the elevation of ancient Florissant?
Here is the method this study used:

1. Find a fossil site that was near sea level, at the same latitude, and in the same time period as Florissant.
2. Use fossil leaves at both sites to determine the ancient average annual temperature of each site.
3. Figure out the rate at which temperature changes because of an increase in elevation.
4. Now calculate.

He concluded that Florissant's ancient forest grew at an elevation similar to today- at about 8,000 feet (2,450 m)

Science is an ongoing process, not just facts. This study shows one of several interpretations about Florissant's ancient elevation, but other studies have reached different conclusions. New research continues to revise our ideas about the world around us.

Evidence of Ancient Climate Change

Elevation is not the only variable that has affected Florissant's climate.
Consider the types of forests that have grown in the Florissant Valley through time.
Its hardwood forests from the Eocene have been replaced by a cooler forest dominated by conifers.
If elevation has remained the same, as this study shows, then what caused the temperature changes and associated forest type changes since the Eocene.

Climate has cooled, but elevation has remained about the same. This study shows the elevation here has remained constant over time. since the Eocene, a cooling global climate is the most likely reason these forests have had to adapt.
 
Artists rendition of ancient Florissant with temperature and elevation differences against modern Florissant
 
To learn more about the ancient climate and climate change you can download our Climate Change Site Bulletin.

Last updated: September 18, 2022

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