 We
started with the lower terrace trails at Devil's Thumb and Palette Spring.
Devil's Thumb is the pointy thing, Palette spring is the hillside covered
in algae and hot water. A ranger once told me that there used to
be more features named after the devil or hell in the early days of the
park, but that the names were changed on many of them. Unfortunate,
but probably the names were getting too repetitious. I assume that
Devil's Thumb is a dormant hot spring cone along the lines of Liberty
Cap or Orange Mound Spring
, one where there was a small but steady flow of water over the years that
built up a steep sided cone. {Remember the browser's back button
for these links to get back to this page}. Palette Spring is kind
of cool too, you can get really close to it. In fact you could walk
through it as the water was flowing over the paved trail in spots. |
 Cleopatra
Terrace. The way I understand it, this feature was one of the stars
at Mammoth in the early part of the 20th century, but was inactive in recent
decades. It was used in guide pamphlets as an example of how activity
at Mammoth shifts frequently. It has now rejuvenated. Angel
Terrace farther down the page has a similar story. |
 This
is a pool at the top of Canary Spring, which is on the Upper Terrace Drive,
a one way road well worth taking. Because at Mammoth you are frequently
looking at a big mound of hot spring deposits from the bottom, sometimes
it is hard to see where the water actually comes out of the ground.
I had a Japanese gentleman ask me while we were lower down the hillside
where the "hot springs" were. I was puzzled at first as we were surrounded
by hot springs. Then I figured out he wanted to see the actual pools
where the water comes out of the ground, so I told him to climb or drive
to this area. Then he was all happy. I don't know if he climbed
or drove. |
 Another
pool at the top of Canary Spring. This one is covered with an unusual
formation called Travertine Ice. Travertine is a rock that is formed
when springs deposit calcium carbonate (the same mineral that makes up
limestone). Mammoth is unusual for Yellowstone because the hot springs
here deposit travertine instead of geyserite (a type of silica) like most
of Yellowstone's other hot springs. This is because here the hot
water flows through beds of limestone. The water is slightly acid
because of the carbon dioxide dissolved in it, and it dissolves lots of
limestone, tons of it per day. After the water reaches the surface
it both cools and becomes less acidic as the carbon dioxide escapes, and
the dissolved limestone gets deposited as travertine. At Mammoth's
terraces the travertine is usually deposited most rapidly at the edges
of the pools, where the water flowing over the edge cools quickest and
looses the carbon dioxide the quickest, which builds up the edges faster
than the bottom of the pool. This frequently leads to a situation
where a series of pools develop that do look sort of like a terraced hillside.
Every now and then for reasons I am not sure of the travertine is deposited
on the surface of the pool like this. I do not know why it does not
sink. But, it does look a lot like ice. |
 Here
a big stream of hot water from Canary Spring is rapidly depositing travertine,
and burying trees. Mammoth's hot springs can deposit a few feet of
travertine in one year, while a typical geyser cone may grow at the rate
of an inch a century. |
 More
of Canary's runoff stream. The frilly formation in the lower left
looked kind of cool, looked like stringy colonies of bacteria I have seen
in other hot springs. I don't know if that is what it actually is
or not. Scientists are just beginning to understand how the bacteria
and algae in hot springs affect the way they deposit minerals. |
 The
very edge of Canary's runoff stream, with some grass getting incorporated
into the travertine. |
 This
is Angel Terrace, at the end of the Upper Terrace Drive. |