"Rainbow Forest Museum" Petrified Forest National Park Travelogue by Paulie_D

(Information from ScienceViews.com)

Imagine a large basin area with numerous rivers and streams flowing through lowland. A lush landscape with coniferous trees up to nine feet in diameter and towering almost two hundred feet tall surrounds you. Ferns, cycads and giant horsetails grow abundantly along the waterway, providing food and shelter for many insects, reptiles, amphibians, and other creatures.

During the Triassic Period (200 - 250 million years ago) the Colorado Plateau area of northeastern Arizona was located near the equator and on the southwestern edge of the landmass known as "Pangea". (Eventually this super-continent separated to create our present continents.) This tropical location resulted in a climate and environment very different from today. Fossil evidence of this ancient land lies in the sediments called the Chinle Formation that is now exposed in Petrified Forest National Park.

Over time, trees died or perhaps were knocked over by floodwaters or wind. Rivers carried the trees into the lowlands, breaking off branches, bark, and small roots along the way. Some trees were deposited on the flood plain adjacent to the rivers and others were buried in the stream channels. Most of the trees decomposed and disappeared. But a few trees were petrified, becoming the beautiful fossilized logs we see today. Most of the fossilized logs are from a tree called Araucarioxylon arizonicum. Two others, Woodworthia and Schilderia, occur in small quantities in the northern part of the park. All 3 species are now extinct.

Petrification:

Some logs were buried by sediment before they could decompose while volcanoes to the west spewed tons of ash into the atmosphere. Winds carried ash into the area where it was incorporated into the deepening layers of sediment. Ground water dissolved silica from the volcanic ash and carried it through the logs. This solution filled, or replaced cell walls, crystallizing as the mineral quartz. The process was often so exact that replacement left a fossil that shows every detail of the logs? original surfaces and, occasionally, the internal cell structures. Iron rich minerals combined with quartz during the petrification process, creating the brilliant rainbow of colors.

That's true. In their 'raw' state the 'logs', whilst having the appearance of fallen trees only have the colors of rocks.

As with any stone, it has to be cut and polished to obtain the true effect.

The picture here shows the opposite sides of a sectioned petrified log.

The log took an entire day to cut through and the left section took 13 days to polish.

Yep, it's a huge example alright. It weighs over 350 pounds.

This log took, if I recall correctly, over 31 hours to cut (using a silicon carbide wire saw) compared to 2.5 hours if it had been made from granite

Venturing outside the Museum there are more specimens of the petrified logs in their natural state.

The rear exit to the musuem find you at the start (& end) of the Giant Logs Trail.

This 4/10 of a mile long trail is improved and fenced and has the highest traffic of any of the park trails. This trail takes you through another area of large logs including Old Faithful, the largest tree in the entire park.

Yes, that's what I thought until I ventured along the Giant Logs Trail.

Here you can see that they do, indeed, look like fallen trees.

Oh well. That's all. Back on the bus.

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