Turn around, and at 0.3 miles, take the miles). Turn left, toward the French Round boiling — and plopping back down to stack right-hand road branch. Barn. Note the eastern end of Graben Dome. up around the spout. On one flow or another, The lava flows on the east side of the road Diamond Craters contains almost every known Park at the edge of the road on the are very complex — they are flank eruptions variation of these features. top of a rise where you can see the from Graben Dome. The geologists haven't 11 divide between Twin Craters at 9 0.7 miles even begun to figure out what exactly hap­ Northeast Dome (11 o'clock) differs from o'clock. Here you get a good view of pened here. the other structural domes, even though it is a Central Dome (10 to 1 o'clock). Remember variation on the same theme. By the time the that Ruptured Raven Ridge (11 o'clock along Almost 1 mile north of Big Bomb initial layer of Diamond Craters Basalt domed the skyline) is part of the original domal arch. 12 Crater, turn into the first road to the up, the layer was relatively cool and brittle. 4.8 miles left and park. The summit rock fractured into numerous, You are looking into the Central Crater nearly parallel, deep fissures — something Complex (10:30 to 11:30) which is a caldera. A On either side of the road are flank flows like corn bread inflating and cracking as it caldera is a depression similar to Crater Lake from Graben Dome. Look at the shallow bakes. Only a few of the but without water. As the supporting magma depression (8:30 to 10 o'clock), filled with fissures have been under the Central Dome blasted out in ex­ spatter features. Observe the spatter ridge measured. One of them is plosive eruptions, the stretched summit rock with the knob of spatter on top at 9 o'clock. 40 feet deep, eight feet collapsed into a caldera. The box-shaped Imagine a fire fountain powered by a very wide and nearly 250 feet depression with rounded ends is about one small amount of steam, showering spatter a long. As the supporting mile long, 3,500 feet wide and more than 200 few feet into the air. As the spatter falls back magma withdrew through feet deep. The Central Crater Complex has around the vent, it welds together into spatter flank eruptions on the more than 30 vents. In fact, the bumps you ramparts or walls (around fissures) and spat­ northern and eastern sides, a small graben see are rims of funnel-shaped craters inside ter rings and cones (around circular vents). formed on the southeastern slope. You can the caldera, similar to the craters at Red see the far wall (11 to 12 o'clock) running Bomb Crater. Near the end of the volcanic ac­ parallel to the skyline. tivity, pahoehoe lava flows formed a moat in­ Driblet spires, side the rim of the caldera. closely related Continue north on the country road and at to spatter 0.7 miles observe the spatter cones resulting Take a look at the dirt (tephra) under the features, from the flank eruptions. These features are sagebrush — it was blown out of the Center sometimes on private property, so please don't cross the Crater Complex. Most of the tephra in Dia­ form on fence. mond Craters came from Central Dome. Even pahoehoe At 1.9 miles, you come to the edge or toe of blocks of Devine Canyon Ash-flow Tuff sur­ flows as a the Diamond Craters flow. Devine Canyon faced from the bedrock beneath the Diamond gaseous spout Ash-flow Tuff can be seen on the hills to the Craters Basalts. The sharp rocks in the road develops, spit­ right. just before you arrive at South Dome are ting thick Pull off the road for a panoramic tephra from Central Dome. globs of mol­ view of the northern half of Diamond ten basalt a 13 Craters. Be safe and watch for traf­ Continue east to Big Bomb Crater (3.9 few feet into the air — like cream of wheat 3.8 miles fic as this stop is on a hilltop. U.S. DEPARTMENT OF THE INTERIOR Bureau of Land Management Burns District Office HC74-12533 Highway 20 West Hines, Oregon 97738 Twin Craters — West Dome Notes and References Although studies by geologists Dr. Bruce Nolf of Central Oregon Community College and Dr. Robert Bentley of Central Washington University have revised ideas on how Diamond Craters was formed, the 1964 paper by Norman V. Peterson and Edward A. Groh entitled "Dia­ mond Craters, Oregon" in 77?e Ore Bin, Vol.26, No. 2 pro­ vides a valuable description of the area. A recent, more technical work that ties Diamond Craters into the regional geology is "High Lava Plains, Brothers Fault Zone to Harney Basin, Oregon" printed in Guides To Some Volcanic Terranes in Washington, Idaho, Oregon and Northern California, Geoloqic Survev Circular 838. It was written by George Walker and Nolf. BLM would like to acknowledge the work of Dr. Pete Mehringer of Washington State University for data on the sediments in Malheur Maar. BLM-OR-GI-89-8-1122.32 A Self-Guided Tour Of: Diamond Craters Oregon's Geologic Gem U.S. DEPARTMENT OF THE INTERIOR Bureau of Land Management Burns District «-. HC74-12533 Highway 20 West ' Hines, Oregon 97738 phonei503) 573-52*41; Text by Ellen M. Benedict, Pacific University Keep your vehicle on on hard-packed road surfaces and obvious parking areas. Certain There's no other place in North America roads and trails are closed for rehabilitation. like Diamond Craters. Be careful or you might spend time stuck in That's the opinion held by scores of scien­ loose cinder, volcanic ash or clay. tists and educators who have visited and If you go hiking, carry drinking water. studied the area. It has the "best and most Watch out for rattlesnakes. If you come upon diverse basaltic volcanic features in the one, stay calm and allow the snake to glide United States and all within a comparatively away. small and accessible area," one geologist summarized. It took thousands of years of volcanic ac­ tivity to form Diamond Craters, but requires Yet visitors with little or no geologic train­ only a few seconds of carelessness or ing will probably see nothing more than acres thoughtlessness to destroy its features. Help of sagebrush and a few lava flows and BLM to protect and preserve Diamond craters. Craters. Please do not destroy or collect This guide will help you to locate and inter­ plants, animals or rocks. pret some of the outstanding features of Dia­ mond Craters that you might otherwise over­ Central Crater Complex look. You won't be an accomplished geologist How To Use This Guide after finishing the tour, but you will have a In the left margin are numbered paragraphs greater appreciation for the area labeled by Start Tour. Mileage begins halfway corresponding to the twelve stops along the between mile post 40 and 41 on one scientist as "a museum of basaltic 40-mile auto tour between State Highway 205 volcanism." 1 State Highway 205 at the junction at Diamond Junction to State Highway 78 at 0.0 miles to Diamond. Turn left. Princeton. The mileage below each number tells the distance from the last stop. Use your Diamond, Oregon, a small ranching com­ Travel and Hiking Hints odometer and the map to help locate stops. munity, was named in 1874 for Mace McCoy's Diamond Craters is located in the high Diamond brand. The nearby craters soon Features at stops correspond to points on became known as Diamond Craters. desert country about 55 miles southeast of a clock face. Imagine that you are standing in Burns, Oregon. It's an isolated place and the middle of a clock face. Twelve o'clock is You'll cross the Central Patrol Road of the some precautions should be taken when the road in front of you and 6 o'clock the road Malheur National Wildlife Refuge and the traveling in the area. behind. If you always align the clock face with Blitzen River at 1.0 miles. The Blitzen River First, Diamond Craters has no tourist the road, you should be able to locate the originates on Steens Mountain, the highest facilities. The nearest place where gasoline features. point in the southeastern skyline. is sold is at Frenchglen or Princeton. Park on the right edge of the soft globs of molten basalt) to violent blasts top of the other one. Be careful not to fall on road. of tephra (solid fragments ejected) thousands the sharp lava. Please, no vehicles are allowed. 2 of feet high. All kinds of activity took place at 2.6 miles On the left side of the road, north of Diamond Craters, creating an exceptional As you return to your vehicle, look closely the marshy area, is a panoramic view of Dia­ basaltic landscape. at the dirt under the sagebrush and notice the mond Craters. Start at the west. Follow the weathering tephra. Between here and the next edge (7 o'clock) of the lava flow east to West More than two-thirds of Diamond Craters is stop, Red Bomb Crater, you will be crossing Dome (8 o'clock). Central Dome (8:30) looks blanketed under basaltic tephra blasted from South Dome which is covered with tephra. like four or five humps along the skyline. vents within the six-mile wide "pancake." You can see tephra from here — it is the decom­ Red Bomb Crater.