Sorry to keep beating this dead horse, but John Foster's claim that there
have been no landscape level changes in the past 90 million years continues
to gall me. About 70 million years ago the place where I live, central
Colorado, was at the bottom of a shallow salt-water sea. To the west were
low mountains all the way to Nevada. Today I'm about a mile above sea level
on the edge of the North American Grasslands. To the West are the Rocky
Mountains, on the average the highest Mountains in North America. Whether or
not this has implications on environmental ethics is interesting. I think
that a sense of place is essential to a sound environmental ethic. I believe
Holmes Rolston devised a simple test to see if an individual was really
aware of their local environment. And, to the point, which I think Foster is
trying to make, that ecosystems do not change much over time, it is well to
remember that ecosystems are not made of angiosperms, they are made up of
individual members of species. While it is entirely true that angiosperms
have been the dominate plant phylum in that period, that means nothing.
Phyla are entirely artificial constructs of a generally accepted taxonomic
system. Phyla do not exist in nature or anywhere else other than the pages
of text books. Phyla do not evolve or change. You cannot go pick a phylum
(you can pick a phlox).

The only level of evolution that makes sense to consider in so far as
environmental ethics are concerned is of species (and the individuals of
that species). So, I suppose Foster's claim that there have been no
evolutionary changes at the level of dominate phyla makes, in a crazy sort
of way, some sense. However, what on Earth it means, you've got me.

I'm attaching a description of the major changes here in Colorado in the
past 90 million years from the Geology Dept. at the University of Colorado.

Steven

 Dada is not dead
Watch your overcoat


At the start of the Cretaceous Period, about 135 million years ago, sands
and gravels were carried eastward over the Boulder area from mountains
rising to the west in Utah and Nevada. At about the same time, a massive
invasion by the sea began in eastern Colorado. The sea entered the central
U.S. from the north and south, laying down a deposit of beach sand along its
edge, known as the lower part of the Dakota group. The group of formations,
including some marine shales, is about 320 feet thick near Boulder. The
lower sandstone of the Dakota is very hard and resistant to erosion, so that
it stands in stark relief above the softer sediments above and below it,
forming the first hogback west of Boulder. The Dakota hogback can be traced
both to the north and south along the eastern side of the Front Range for
hundreds of miles.

The next 70 million years of Cretaceous time were marked by several advances
and retreats of the sea. The deposits associated with these episodes of
marine flooding consist of shale, sandstone, limestone, and some beds of
coal. The environments suggested by the rocks include the deep sea, sandy
beaches, and coast swamps. Names applied to the various formations are (from
oldest to youngest): the Benton Shale, Niobrara Limestone, Pierre Shale, Fox
Hills Sandstone, and the Laramie Formation. Together these formations total
over 10,000 feet of sediment. Fossils are abundant in many of these units.
These strata are generally soft and easily eroded. The city of Boulder and
the National Center of Atmospheric Research (NCAR) are built on the Pierre
Shale. The fresh Pierre is gray, soft, and best seen in fresh roadcuts and
ditches.

At the end of Cretaceous time, about 70 million years ago, the sea slowly
withdrew to the northeast. It left behind vast swamps, from which the coals
of the Laramie Formation formed. The withdrawal of the sea took about 10 to
15 million years.

Cenozoic Time (0 to approximately 65 million years ago)

During the late Cretaceous and early Tertiary time, mountain building began
again in Colorado. As the mountains were uplifted, swiftly flowing streams
carried floods of debris downward to the plains. Hot magma invaded the older
rocks of the mountains, and the forces of mountain building caused the rocks
to be greatly deformed. Rich deposits of metallic ores were precipitated as
hot mineralizing waters flowed from the magmas through the cracks in the
rocks. It was at this time, in the early and middle Tertiary Period, that
most of the valuable deposits of metallic ores were formed in Colorado.

Where the magma reached the surface of the earth, it spewed out in the form
of volcanic eruptions. Only the scattered remains of lava flows can be seen
in the Boulder area, such as on the tops of North and South Table Mountains
near Golden.

It was during this time of mountain building that the Fountain Formation was
steeply tipped to form the Flatirons along the east front of the mountains.
The thick Pierre shale was also bent upward under the present site of
Boulder.

Active mountain building continued throughout the remainder of Tertiary and
Quaternary time. It is probable that the Rockies attained their greatest
height in the early Tertiary Period, about 45 million years ago. Those peaks
were later lowered by erosion.