Welcome to You Ask Andy

Michael Abrams, age 10, of Beachwood, Shzo, for his question:

 How did the Petrified Forest become petrified?

The Petrified Forest is a beautiful barren land of color and hills and sandy plains. Next door is the gaudy Painted Desert. Some 145 square miles of this scenic territory has boon set aside as a National Monument. Countless visitors drive to eastern Arizona to admire this two‑in‑one spectacle every year.

But this land was not always a desert of bare, barren rocks. In the late Triassic Period, between 160 and 170 million years ado, it was a well‑watered forest land. The sea, which is now the distant Gulf of Mexico, lapped over southern Arizona at that time. Northern Arizona was shore line where at least one gushing river flooded into the sea.

Groat trees, sumo of them with giant trunks, grew in what is now the barren desert. From time to time one of these huge trees fell to the ground. Some were struck down by arrows of lightning, others collapsed with the burden of years. And from time to time the gushing river overflowed its banks into the woodland. The fallen giants were floated. along on the flood. They were dumped in a valley where they formed a kind of log jam.

This happened year after your and. logs were buried deep in the sandy silt. The wood was steeped in stagnant water nnd stagnant water contains little or no oxygen. Bacteria and tine bugs, which ordinarily cause wood to rot, cannot live or breathe in it. The logs, buried and half buried in the stagnant swamp, could not decay.

The stagnant water dissolved chemicals from the rocks. It seeped into the pores and cells of the fallen logs and dissolved the woody tissues end the chemically rich water made a swap. For every particle of wood it dissolved. and toted away, it left a particle of stony chemicals. Bit by bit the wood was replaced by stone.

The exchange was made in tiny clotail, a molecule of stone for a molecule of weed. In this way the stone built up a perfect copy of the woody cells of the fallen tree. Mlost of the stony material Was silicate and the trues were copied in opal, agate, carnelian jasper and onyx. These are glossy and colorful semi‑precious materials. There were also dissolved metals in the stagnant water. These added rich tones of rust, red and flaming orange to the petrified wood.

Hundreds of ancient tree trunks were turned to stone in the stagnant swamp. Finally the sea receded and the silty area became a dry, barren desert. Only the petrified trees remained to tell of the proud forest that once grew there.

Our Petrified Forest contains the largest and most beautiful collection of petrified wood in the world. Giant hunks of semi‑precious stone lay strewn on the ground and no one knows how many are buried below. The petrified wood can be cut and polished to a high gloss. And, with a magnifying glass, you can see, it is a perfect copy of woody tolls. The beautiful cell structure is replaced, bit by bit, with semi‑precious stone.

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