Geology

Jake Roe and Boyd walker, Kinross-Delmar Mining Co.
and
Dennis Walker and Hilary Heller, Owyhee Watershed Council & Teague Mineral Co.

Did you know? Much of the land in Malheur County
was formed by volcanic eruptions. The cliffs and local soils that you see around you
are various layers of basalt and rhyolite.

2011 images available for viewing here
Click on thumbnails to view an enlarged image.

     

Everything that we use is either grown or mined. You might recognize silver for its use in wiring, electronic components and jewelry. But, did you know that everything that is in your cars, food, clothes, homes, schools, and stores has been extracted from rocks or grown? The cement used to build the Owyhee dam; the gravel, sand, and steel were mined from the ground.

There are lots of stages in mining. What are they? Exploration, development, construction, mining, processing, sales and reclamation of the mined site are all important stages.

Panning for gold requires patience. You need water in one side of the gold pan to work most of the material out of the pan. Swirl the pan around to remove the lighter rocks from the pan. The gold is heavier than the sand and rock and it will be int he bottom of the pan.

Owyhee Makes Mining History

In 1863, gold was discovered in Jordan Creek in the Owyhee Mountains. In the early mining period, from the 1860's to 1940, about 15 tons of gold and 500 tons of silver were mined from the Silver City area of the Owyhee Mountains. The rocks were crushed; the gold and silver were separated and then melted into gold and silver bars.

The Delmar mine opened near Silver City in 1976 and operated until 1998, extracting an additional 25 tons of gold and 1500 tons of silver! The Delmar Mine covered more than 800 acres.

Today the land of large scale mines like the Delmar are being reclaimed. Pits are partially back filled and the land is seeded. Grass grows and the area starts to look more natural. At the Delmar mine, blue bunch wheat grass, Idaho fescue, Canada bluegrass, blue flax, and thick spike wheat grass have been planted.

Clint Shock's Discussion of Geology

Suppose you are standing on the east shore of Payette Lake, Idaho. In front of you are deep blue waters and mountains beyond in the west. What made the lake?  What lies directly behind you to the east? Stop now and look.

The hills immediately behind you to the east have no solid bedrock but are mounds of coarse gritty soil and round boulders. Most of the boulders are granite but a few are even dark gray throughout. What has gone on here? Stop now and look.  What can you find?

By asking yourself these questions and searching for answers like a detective, you are doing the work of a geologist. Geologists use clues hidden in the rocks and other deposits to try to piece together understanding of the history of planet earth. But the earth yields up its secrets grudgingly. It has taken thousands of geologists many decades to piece together what is known. Each major geological event can leave traces, which remain even when most of the signs are destroyed by subsequent events.

The geological history tells of an earth without higher plants and animals, of ancient seas whose bottoms are now raised up into mountain ranges and of may impressive dinosaurs that are long extinct. Each rock and deposit, however unimpressive, has an ancient hidden story. Can we discover their stories?

Ancient continent

Many geologists now believe that much of the earth's crust that is currently divided into continents was once arranged in a super large continent called Pangaea. This large land mass is thought to have started to break apart about 250 million years ago.

Plate movements

The breakup of Pangaea and the movement of today's continents are explained by the geological theory called "plate tectonics". According to this theory, plates of the earth's crust (about 60 to 90 miles thick) move slowly on the more liquid mantle beneath. Convection currents in the mantle drive the plates.

The continental plate of North America is thought to be moving westward in relationship to the mantle beneath. The hot spot at Yellowstone seems to be moving to the east through the continent. The hot spot is thought to be a feature of the mantle beneath the earth's crust. Masses of deep volcanic ash like that produced by the huge volcanoes of Yellowstone can be found across southern Idaho and into the Owyhee uplands in Malheur County, Oregon. Your can explore deep beds of volcanic ash (similar to the ash of Yellowstone) that have been eroded by water and wind into fantastic forms at Leslie Gulch, the Honey Combs, Carlton Canyon, and the Painted Canyon all in Malheur County. These formations can also be found to the east in southern Idaho.

Idaho Batholiths:

bath·o·lith n. A large mass of igneous rock that has melted and intruded surrounding strata at great depths.

At one time the western edge of what is now North America was about lined up with the western edge of Idaho. The encounter of the continental plate with the northern Pacific Ocean plate is thought to have created the granitic mountains of central and northern Idaho. The part of the Idaho batholiths in central mountains is called the Atlanta batholiths.

Large islands docked on coast. Through plate movements, large hunks of crust are thought to have been added to the west coast of North America. Northeastern Oregon and parts of Washington are thought to have been added like large barges docked on western Idaho.

Basalt flows

Starting about sixteen to seventeen million years ago, huge volcanic basalt flows were emitted that covered much of the low lying interior of the Pacific Northwest. Basalt and ash flows filled Malheur County. Recent flows like the ones at Jordan Craters, Oregon, and Craters of the Moon, Idaho, have occurred, but they have been much smaller volcanic events.

Gold and thunder eggs

Many deposits of rarer elements and minerals occur within major formations. The unmined gold at Grassy Mountain and other locations in the Owyhee uplands is thought to have be deposited by hot water over millions of years following the volcanic eruptions. Over time minerals can be concentrated and crystals can form. You can find a ready source of small geodes or "thunder eggs" within a mile north and south of the Succor Creek State Park campground along the creek (foot access only). Be careful of the poison ivy

Ice ages

Over the last several million years, several ice ages have formed glaciers. The glaciers have distinctly carved high mountains into U shaped valleys, steep circs at the upper end of glaciers, and built up moraines. Ice age rock carving is obvious in the Wallowas, central Idaho mountains near McCall, the Saw tooth Mountains, the Steens Mountains, and elsewhere. The valleys are deep Vs, shaped by running water, not glaciers.

Lake Bonneville

Following the last ice age, geologists believe that much of the Inter-mountain West was flooded with water from melted ice. At huge lake is believed to have formed as a much enlarged Great Salt Lake called "Lake Bonneville". Lake Bonneville is important to the Snake River! Lake Bonneville spilled through the mountains at Red Rock Canyon and rushed down the Snake River in a catastrophic flood. The upper Snake River bears the scars. The Treasure Valley near Ontario was temporarily flooded to a considerable depth, and a thick layer of silt soil was deposited. Look for the silt. Clear lines of lake bottom silt deposits are visible on the road cut on the south edge of the Malheur Experiment Station, Ontario, Oregon and many other locations. The flood was 120 to more than 400 feet deep through Hells Canyon on the Snake River.

Recent volcanoes

You can explore recent volcanic activity.  There have been relative recent lava flows in South Eastern Oregon at Jordan Craters near Jordan Valley in Malheur County, at McKinsey Pass between Sisters and Eugene, and at the Craters of the Moon National Monument in Idaho. You can find all sorts of lava, lava tubes and Cinder forms to explore. When exploring lava tubes, use flashlights and safety precautions.


The Owyhee Watershed Council's educational activities are supported by the
Oregon Watershed Enhancement Board.

For further information please contact:
Nicole Sullivan
Owyhee Watershed Coordinator
(541) 372-5782
nsullivanowc@qwestoffice.net