hundred years ago, William "Strata" Smith was traveling the length
and breadth of England, creating a map that changed the world.
same time, Captains Meriwether Lewis and William Clark and the Corps
of Discovery were traversing the length of North America, creating
other maps that changed the world as well.
Lewis and Clark began a voyage of discovery with 45 men, a keelboat,
two pirogues and a dog. They departed from Camp Wood in what was
to become Illinois to explore, at the behest of President Thomas
Jefferson, the lands involved in the Louisiana Purchase from France.
Clark were ordered to write accounts of all they did, each species
encountered, details of the cultures they met, maps of the land
— everything. They traveled over a three-year period through lands
that later became 11 states.
Smith's human tale of endurance, dedication and achievement recently
has been in the spotlight with the publishing of Simon Winchester's
book The Map that Changed the World, chronicling the creation and
presentation of the first geologic map.
the next two years, the bicentennial of Lewis and Clark's epic exploration
of the Western United States will be celebrated in numerous festive
and education events over the 3,200-mile trail from St. Louis to
the Pacific Ocean.
of the educational opportunities is the AAPG Lewis and Clark Geotour:
Marias River to Gates of the Mountains, Montana, which will be offered
will be led by William Hansen, of Jireh Consulting Services in Great
storyteller, Hansen said the Geotour, which begins and ends in Great
Falls, includes guided trips to the Great Falls of the Missouri
River, White Bear Island Portage Camp, historic Fort Benton Missouri
River steamboat wharf and a cruise boat trip through Lewis and Clark's
"Gates of the Mountains" canyon in the Montana Thrust Belt.
also includes outfitted white water and canoe trips.
way there will be plenty of tales of the exploits — and a lot of
geology. The exploration party spent over a month in the Great Falls
area portaging the series of five, well, great falls.
at Lewis and Clark sessions at last year's Geological Society of
America annual meeting in Seattle, Lewis was the biologist/botanist
who wrote in his journal in a narrative and descriptive style. Clark
was the mapmaker/river man who wrote facts readably, with capitalization
for emphasis and some inventive phonetic spelling.
having been tutored in the scientific method and observational skills,
their journals contain hundreds of informative geological, geomorphologic,
sedimentological and economic geology observations, Hansen said.
good," he commented, "considering the science of geology hadn't
even been invented yet."
Clark's description of Giant Springs, June 18, 1805:
on up the river a little more than a mile to the largest fountain
or spring I ever saw and doubt it is not the largest in America
known. This water boils up from under the rocks near the edge of
the river and falls immediately into the river eight feet and keeps
its color for (about a) mile which is immensely clear and of a bluish
what we know now: At Giant Springs - Fresh water flows out of springs
at 134,000 gallons per minute (1.93 million barrels of water per
day) from a regional fracture system that conducts the water from
the Mississippian Madison Limestone aquifer to the surface.
the mountains on July 17, 1805, Clark described the rocks we now
know are part of the Late Cretaceous Adel Mountain volcanics as:
high precipices oblige all the party to pass and repass the river
from one point to another. The river confined in many places in
a very narrow channel from 70 to 120 yards wide. Bottoms narrow
without timber and many places the mountains approach on both sides;
the river crooked, the bottoms narrow, cliffs high and steep. I
ascended a spur of the mountain which I found to be high and difficult
of access, containing pitch pine and covered with grass."
the stretch of the river known as the Gates of the Mountains, Lewis
writes on July 19, 1805:
we entered much the most remarkable cliffs that we have yet seen.
These cliffs rise from the water's edge on either side perpendicular
to the height of 1,200 feet. Every object wears a dark and gloomy
aspect. The towering and projecting rocks in many places seem ready
to tumble on us. The river appears to have forced its way through
this immense body of solid rock for the distance of 5-3/4 miles
and where it makes its exit below has thrown on either side vast
columns of rocks mountains high.
appears to have worn a passage just the width of its channel or
150 yards. It is deep from side to side, nor is there in the first
three miles of this distance a spot except one of a few yards in
extent on which a man could rest the sole of his foot. Several fine
springs burst out at the water's edge from the interstices of the
rocks. It happens fortunately that although the current is strong
it is not so much so but what it may be overcome with the oars,
for there is here no possibility of using either the cord or setting
late in the evening before I entered this place and was obliged
to continue my route until sometime after dark before I found a
place sufficiently large to encamp my small party. At length, such
a one occurred on the larboard side where we found plenty of light
wood and pitch pine. This rock is a black granite below and appears
to be much lighter color above and from the fragments I take it
to be a flint of a yellowish brown and light creamy-colored yellow.
From the singular appearance of this place I called it the gates
of the rocky mountains."
said the rocks Lewis described here are the Mississippian Madison
Limestones, exposed in the footwall of the Eldorado-Lewis Thrust
system in the Montana Thrust Belt.
upstream, the Geotour will also examine the Precambrian Belt Series
rocks thrusted over the Madison and exposed in the hanging wall
of the thrust. Lewis describes the limestones as being dark and
foreboding, which is probably a result of his seeing the rocks initially
in the deep canyon in the early evening after a rain storm, which
tends to make the rocks look darker.
the Geotour spots includes the Sacagewea Sulphur Springs, so-called
because several gallons of the mineral-rich water was able to break
a fever the courageous Indian princess had contracted.
their return trip, the explorers took a wrong turn north into hostile
tribal territory, which caused a backtracking again to the area.
the GSA sessions noted that the captains made some of the geological
notations in greater than 45 percent of their daily journal entries
in the out-bound 320 days of their journey, and exceeds 60 percent
if their sedimentological observations are noted.
a remarkably complete and relatively continuous account of the geological
terrain of the expedition round," presenter John Jengo said, "and
one that is simple to recognize and retrace 200 years later."
about the Lewis and Clark Geotour, contact the AAPG education department,
or visit the AAPG