December 2020
M T W T F S S
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31

Blog Posts

Klammath Forest Fires

The first forest fires occurred about 470 million years ago. Plants had only recently moved from the water to the land, after the blue-green algae had filled the atmosphere with oxygen.

13% oxygen is the lowest level the atmosphere will support fire, and shortly after the atmosphere reached that point, the first fires probably happened.

Wildfire is recorded, by the presence of charcoal. The first widespread charcoal in the fossil record are during the Late Silurian, about 420 million years ago.

The evidence of wildfire is pretty much continuous since then, with a few possible gaps for unknown reasons.Charcoal after a forest fire

About 6 to 7 million years, grasses diversified and spread across the landscape. Coinciding with this there was an increase in the apparent frequency of wildfire.

During the Carboniferous, charcoal is fairly common. The great forests that formed the coal seams that give the age its name, are composed of up to 20% charcoal.

At the end of the Permian and beginning of the Triassic, about 252 million years ago, there was a very large drop in the oxygen levels in the atmosphere. This was probably due to a huge die-off among plants, as well as animals. Up to 96% of marine life, and 70% of land life became extinct.

Without the oxygen, or fuel, the rate of fires dropped as well.

ash on car during California wildfires September 2020It took until the late Jurassic until wildfires were again significant enough to make a significant mark in the fossil record.

Fossil charcoal is called fusain, and is silky, and crumbly, and may be massive or in thin layers.

 

<<<Future Fusain. Ash on a car in California, September 9, 2020. David Gallaher photo.

Charcoal after a forest fire. Antoine Rault photo. >>>

 

Photo at top: Forest fire in the Klamath Mountains. Matt Howard photo.

ammonite sculpture

Ammonites were a huge group of now extinct cephalopod mollusks, relatives of the squids, octopuses, and nautilus.

Ammonites lived from the Devonian to the end of the Cretaceous, 408 to 66 million years ago. They became extinct with the non-avian dinosaurs at the end of the Cretaceous.

They were named by Pliny the Elder (23-79 CE), who called them “Horns of Ammon,” Ammon being an Egyptian god pictured with curled rams’ horns.

The fossils are their curled shells. Like the nautilus, ammonite shells have interior dividers between chambers. The dividers in most species were very complicated in their construction. The curves and shapes in them acted to increase their strength, and the strength of the shell as a whole.

This made them more resistant to predators like mosasaurs, and to water pressure at greater depths. Many shells have been found with the teeth marks of mosasaurs (marine predatory reptiles).

Some ammonite species got up to 6.5 feet (2 meters) across the spiral. They came in many styles of shell, from the tight coil seen in this specimen to loose curvy open spirals.

Like the nautilus, the ammonites were able to move gas and liquid around among the chambers to allow them to float in the water column.

Ammonites were predators, and probably also were able to “jet” by holding and pushing water out of their bodies, like their modern relatives.

There is some evidence that ammonites had ink sacs like modern cephalopods, but it is far from settled. Most people who study them say they did not.

Also like the nautilus, the animals would have tentacles and a head that would stick out of the opening in the shell. The rest of the body was in the first few segments of the shell.

This Ammonite in the Museum’s collection is Devonian, about 350 million years old.

Devonian ammonite and living nautilus

H is for Hardness
A new little video on YouTube for you today.
An brief introduction to the Mohs Hardness Scale for Mineral Introduction.
Please watch, enjoy, like, and subscribe!
Hardness for Mineral Identification Video Thumbnail

Glacial erratic in alaskaGlacial Erratics are rocks that have been transported by glaciers and left behind in a new place when the glacier retreats. Almost always the erratics show a different geology than the place they are left.

Some are moved a very short distance, but some have been moved many many miles.

Eastern Washington is one place glacial erratics can be found. The results of erratics can be found on the rocks in New York's Central Park. Many of the boulders there have scatches on their tops - grooves left by other boulders that were bounced along above them in the ice tha covered the northeast 12,000 years ago.

This erratic is 20 ft high gneiss, left behind by Steller Glacier, in Alaska. The ground is covered by sediment also deposited by the glacier.

USGS photo

 

Ruby Mountains-East Humboldt Mountain Range is east of Elko, Elko County, in northeastern Nevada.

Lamoille valley in the Ruby Mountains

The range lies about half way between the Sierra Nevada and the Wasatch Mountains Ruby Dome, the highest of the peaks, stands 11,249 feet, about 5,500 feet above the valley. The Lamoille Glacier carved the valleys of this range.

The glacier reached its maximum during the Illinoian Stage of the last ice age of the Pleistocene, 191,000 to 130,000 years ago.

The mountains are a metamorphic core complex. There are middle and lower crust metamorphic and igneous rocks that make up the mountain cores. The lower crustal rocks are toward the north end of the range.

The basins around the mountains are filled with sedimentary rocks.

The higher elevations are well known to birders as the only place in the western hemisphere where you can find the Himalayan Snowcock, which was introduced here.

The image was taken at the Lamoille Glacier Overlook. 1,000 foot sheets of ice carved the valleys seen here. Bob Hole photo.