JULY 1978 VOLUME 6 - NUMBER 3 A PLBLICATION OF THE DEPARTMENT OF NATURAL RESOURCES WASHINGTON GEOWGIC NEWSLETTER BERT L.COLE COMMISSIONER OF PUBLIC LANDS RALPH A BESWICK, Supervisor VAUGHN E. LIVINGSTON,JR.,State Geologist DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGY AND EARTH RESOURCES DEPARTMENT Of NATURAL RESOURCES, DIVISION OF GEOLOGY AND EARTH RESOURCES, OLYMPIA, WASHINGTON, 98504 LOCATION MAP : DIVISION OF GEOLOGY AND EARTH RESOURCES DEPT. SOCIAL AND HEALTH SERVICES t ~ i~L f ...J ~ i ,...... N g a: ~ ~OGY ANO EARTH <t tt RESOURCES D u -, t STATE CAPITOL ... TACOMA S~TILE- IDEPT. HIGHWAYS CITY CENTER FREEWAY EXIT PORTLA~ STATE CAPITOL EXIT Vaughn E. (Ted) Livingston, Jr., Supervisor Geologic Staff J. Eric Schuster, Assistant Supervisor Minerals and Energy Geologists Land Use Geologists Carl McFarland James G. Rigby Allen J. Fiksdal Keith L. Stoffel Clint Milne Glennda B. Tucker Kurt L. 0th berg Gerald W. Thorsen Wayne S. Moen Ellis R. Vonheeder Pamela Palmer Weldon W. Rau Charles W. Walker Regulations and Operations Surface Mined Land Reclamation and Oil and Gos Conservation Act Donald M. Ford, Assistant Supervisor Publications: Library: Laboratory: Secretaries: Loura Broy Connie Manson Arnold W. Bowman Patricia Ames Keith Ikerd Cherie Dunwoody Wonda Walker Kim Summers Pamela Whitlock Mailing address: Deportment of Natural Resources Division of Geology and Earth Resou rces Olympia, WA 98504 (206) 753-6183 ORIGIN OF THE GRAND COULEE AND DRY FALLS by Ted Livingston Washington State hos many interesting geo­ original terrain until in the Grand Coulee area it was logic features. Among the more outstanding dre the completely buried. During the course of these erup­ Grand Coulee and Dry Falls . tions, as the molten rock came pouring out on the Some 25 million years ago, at the beginning surface, the earth's crust gradually sank down into of the Miocene Epoch, the area we now know as the the space left by the rising magma. Columbia plateau was a fairly rough mountainous This subsidence of the earth's crust, along terrain made up generally of granite in the northern with the accompanying outflowing of lava, produced port, metamorphic and granitic rocks in the eastern one of the largest basalt-filled basins in the world; in port, and volcanic and sedimentary rocks in the the center of the basin, the basalt probably reaches southern and western ports. The streams that drained o thickness of 10, 000 feet or more. th is area, as well as regions to the west, north, and Just how long the span of time was between east, had probably joined on their way to the sea the first ond lost of these eruptions is not known; how­ and formed the primeval Columbia River. ever, it probably covered 10 to 15 mill ion years. Some time during the Miocene Epoch, per­ Likewise, the time differential between individual haps only slightly more than 10 mil I ion years ago, eruptions in the Dry Fol ls area is not known; it may many large, deep faults developed in the area of the have been a few hours, days, weeks, years, or thou­ Co lumbia Basin. These faults, or fissures, were so sands of years. deep, in fact, that they reached through the crust ond The lava flows, as they issued from the fis­ intc the eorth's mantle (50 miles .±). These deep cracks sures, spreed over the area; they first filled the stream served two functions; one was that they produced a valleys, forming dams that in turn caused impound­ lowering of pressure at great depths allowing the rocks, ments or lakes. As time passed, the streams eventually which were hot enough to melt but were formerly under circumvented the lava dams and found new courses, too great a pressure to do so, to become fluid or molten. only to be redammed and pushed out of their channels Secondly, the creeks served as chonnelwoys for the by new floods of lava. This constant bottle between newly molten rock or magma to speed to the surface the streams of water end lava floods continued, unti I where it flowed out as a volcanic eruption. Each eventually the streams were more or less consolidated layer or bed of basalt in the cliff walls of the coulee into one large river, the Columbia, and forced to represents a separate volcanic eruption. As the erup­ skirt the north edge of the orea of lava flows. The tions continued, the lava flows began to cover the abundant lake deposits of si It, sond, ond clay found Cover Photo Dry Fol ls and the Upper and Lower Grond Coulees were excavated by tremendous discharges of glacial melt waters. After retreat of the floodwaters and reoccupation of its present course by the Columbia River, Dry Falls was left as we see it today, a magnificent series of arcuote escarpments and lcke-fi I led plunge pools. between different basalt flows, as well as the ancient the large vertical columns so noticeable in many of lava-filled stream channels that ca'n be seen in many the coulee walls. of the coulee wa lls, bear mute witness of the struggle As the Miocene Epoch drew to a close, the that went on between these two opponents. great fissure eruptions became fewer and fewer, unti I The lakes that were formed by the lava dams at lost all volcanic activity in the area of the Colum­ no doubt served as population centers for plants and bia plateau stopped . Then commenced a period of animals that existed during that time. It is from the time when tremendous compressional forces within the sediments that were deposited in the lakes, and some­ earth began to slowly up-fold ports of the plateau into times from the lava and polagonite (o yellowish- brown, long narrow northwest- to east-west trending ridges clayl ike material formed by the alteration of volcanic cal led anticlines. Some of these ridges are the Horse­ gloss) beds that immediately overlie them, that the heaven Hil Is, Rattlesnake Hills, Yakima Ridge, evidence of that life is found. Fossil leaf impressions, Untanum Ridge, Saddle Mountains, and Frenchman petrified wood, fossil insects, and bones of vertebrate Hills. During this time, a great monoclinol fo ld was animals hove all been found in, or associated with, pushed up, trending east-west through the Beesley these ancient lake beds. Hills to Ephrata, where its trend became northeast to One of the most Uhvsual fossils ever found about Hartline. Simultaneously, a sma ll asymmetrical in the Columbia plateau is a mold of a small rhinoceros, east-west trending anticline was pushed up in the Soap commonly known as the "Blue Lake Rhino." It was Lake area. During this period of folding, the whole locclted in Jasper Canyon in 1935, /ust below Dry plateau was tilted slightly to the south by the general Falls, by o group of hikers. The mold is preserved in uplift of the mountainous area to the north. pillow basalt that overlies a thin sand bed. Probably The climate during Miocene (25 to 10 mi llion the rhino, already dead and lying in a small pond, years ago) and Pliocene {10 to 1 million years ago) was covered by molten lava that hod chi I led when it times was temperate. Such trees as the bold cypress, flowed into the water and formed basalt pillows and chestnut, beech, fig, sycamore, tulip tree, magnolia, pologonite around the rhino without cremating it. sassafras, hickory, poplar, birch, elm, and maple a ll The pillows were light enough so they didn 1t crush the flourished in the cou lee area. Toward the lost port of animal bu!' were able to pock in around the carcass the Pliocene the climate began to cool and what we sufficiently well to preserve the rhino's shape. Pale­ coll the ice age began. During this period, vast ontologists made o cost of the mold and reconstructed continental ice sheets slowly pushed their woy down the rhino. from the north country, overwhelming everything in The basalt flows that make up the Columbia their path except the highest mountain tops. These plateau are in themselves somewhat of a wonder. peaks stuck above the surface of the ice like islands Most magmas, as they pour out of a volcano, form from the sea. relatively sma ll lava streams that rush down the sides The ice sheet pushed down out of Canada, of the volcano, no matter whether it be o strato­ across the Okanogan Highlands, and into the northern vol cano like Mount Ra inier or a shield volcano like port of the plateau. One lobe advanced as for south Mauno Loa. The lavas of the Columbia plateau, as Coulee City, forming on ice dam across the however, were extremely fluid and spread out in Columbia River at the present site of the Grand Coulee large puddles or lakes. Some geologists who hove Dam. At this position the ice remained stagnant; that studied them suggest that several of these lava lakes is, the rote of melt was equal to the rote of advance may hove been more than 100 miles across their long­ for many years, as evidenced by the large terminal est dimension. As the lava flows cooled and solidified, moraine (a more or less sinuous ridge of boulders, many of them developed a joint system that produced grove I, sand, and mud) that formed at the ice front. 2 This moraine stretches southeastward from the lower cataract retreated back upstream to the present site end of the Lake Chelan across the Big Bend country of Dry Falls before the original channel of the Colum­ almost to the southern end of Grand Coulee, then bia River was freed of ice, al lowing the river to return turns to the northeast and parallels the west rim of to its normal stream course.