Text by Ellen M. Benedict, 1985 Features at stops correspond to points on a clock ago, a huge mass of hot gases, volcanic ashes, bits face. Imagine that you are standing in the middle of a of pumice and other pyroclastics (fire-broken rock) Travel And Hiking Hints clock face. Twelve o’clock is the road in front of you violently erupted. The blast – greater than the May and 6 o’clock the road behind. If you always align the 18, 1980, eruption of Mt. St. Helens – deposited a Diamond Craters is located in the high desert country clock face with the road, you should be able to locate layer of pyroclastics 30 to 130 feet thick over an area about 55 miles southeast of Burns, Oregon. It’s an the features. almost 7,000 square miles! isolated place and some precautions should be taken . when traveling in the area. Start Tour. Mileage begins halfway Pyroclastics are between milepost 40 and 41 on State normal behavior Diamond Craters has no tourist facilities. The nearest Highway 205 at the junction to Diamond. for magmas place where gasoline is sold is at Frenchglen. Turn left. (subsurface That’s the opinion held by scores of molten rocks) Keep your scientists and educators who have visited Diamond, Oregon, a small ranching community, was of rhyolitic (a vehicle on named in 1874 for Mace McCoy’s Diamond brand. volcanic material and studied the area. It has the “best and hard-packed The nearby craters soon became known as Diamond related to granite) most diverse basaltic volcanic features in the road surfaces Craters. composition. The and obvious United States and all within a comparatively silica (similar to parking areas. small and accessible area,” one geologist You’ll cross the Central Patrol Road of the Malheur Oregon beach Certain roads summarized. National Wildlife Refuge and the Blitzen River at sand) content and trails are 1.0 miles. The Blitzen River originates on Steens is so high in the closed for Twin Craters West Dome at stops 8 and 9. Mountain, the highest point in the southeastern rhyolitic ash – 75 Yet visitors with little or no geologic training rehabilitation. skyline. percent for the Devine Canyon Ash-flow Tuff – that the Malheur Maar at stop 10. Be careful or will probably see nothing more than acres of magma is very stiff and pasty. Great pressure builds you might spend time stuck in loose cinder, volcanic sagebrush and a few lava flows and craters. Park on the right edge of the road. within the volcano and eventually it explodes. When ash, or clay. On the left side of the road, north of the pressure doesn’t build up, rhyolitic magma squeezes marshy area, is a panoramic view of up, like toothpaste, building a bulbous, steep-sided This guide will help you to locate and If you go hiking, carry drinking water. Watch out for Diamond Craters. Start at the west. plug dome over the vent. interpret some of the outstanding features of rattlesnakes. If you come upon one, stay calm and Follow the edge (7 o’clock) of the lava flow east to allow the snake to glide away. Diamond Craters that you might otherwise West Dome (8 o’clock). Central Dome (8:30) looks If you want to look at Devine Canyon Ash-flow Tuff overlook. You won’t be an accomplished like four or five humps along the skyline. Graben more closely, stop at the roadcut just before the It took thousands of years of volcanic activity to form geologist after finishing the tour, but you Dome (10:30) wears the crown of juniper trees. The junction (4.1 miles) where you turn left to Diamond Diamond Craters, but requires only a few seconds two red cinder dish-shaped craters (9:30) midway Craters. The un-weathered rock is light gray. will have a greater appreciation for the area of carelessness or thoughtlessness to destroy its below Graben Dome are part of South Dome. labeled by one scientist as “a museum of features. Help the BLM to protect and preserve Park on the rise at the right edge of the Diamond Craters. Please do not destroy or collect basaltic volcanism.” As you can tell from the map, Diamond Craters road, just past a junction coming from the plants, animals, or rocks. resembles a thin, rocky pancake with a few bumps. east. You should be able to see the road to There is only a 550 foot range from the lowest to Diamond Craters disappearing in an S-shaped bend. highest point. Elevations are from 4,150 to 4,700 feet above sea level. You are viewing the contact between the Diamond Crater Have you noticed the rimrock on the buttes and the basalts (dark lava flow, 10 o’clock) How To Use is Guide tablelands to the west, south, and east? The layer is and the Devine Canyon Ash-flow In the left margin are numbered paragraphs the Devine Canyon Ash-flow Tuff. This weathered, Tuff (reddish-brown, 12 o’clock). If corresponding to the thirteen stops along the 40-mile reddish-brown layer may look solid, but it is actually a hole were drilled through Diamond auto tour between State Highway 205 at Diamond composed of many thin layers of ash and rock all Craters basalts, it would probably Junction to State Highway 78 at Princeton. The compacted together – something like caramel corn. hit lake sediments and Devine Canyon Ash-flow Tuff. mileage below each number tells the distance from Can you visualize the down-tilted layer extending the last stop. Use your odometer and the map to help The rimrock came from a volcanic vent located under under the lava flow? locate stops. present-day Burns, Oregon. About 9.2 million years How did Diamond Craters form? Park immediately on the hard-packed the other flow. To prove this, walk down and follow activity resumed in a series of smaller explosive Sometime in the last 25,000 years cinder by Big Bomb Crater, a restored the contact between the two flows to see which one is eruptions inside the big crater, forming the funnel- (geologists are not sure just when), cinder pit. Here you can see cored bombs, on top of the other. Be careful not to fall on the sharp shaped craters. Which vent erupted last? molten basalt spilled from deep which are marble-to-baseball-sized rocks. lava. Please, no vehicles are allowed. cracks in the earth called fissures, As the hot magma rises up through water-soaked Now look at the bombs scattered along the parking then flooded in a thin layer over a layers, the water instantly changes to steam, causing As you return to your vehicle, look closely at the loop road. You may see a breadcrust bomb. Cooling relatively dry lake bed. Before the magma to explode and hurl rock fragments in the air. dirt under the sagebrush and notice the weathering basaltic globs became airborne. The surface chilled as initial layer cooled completely, more basaltic magma The fragments fall back into the developing cinder tephra. Between here and the next stop, Red Bomb the inside gases, mostly steam, expanded. That caused injected underneath, creating six arching structural cone and roll down into the vent. This is repeated Crater, you will be crossing South Dome, which is the outside of the globs to crack, forming a breadcrust domes. several times as the fragments become coated with covered with tephra. texture. Again, please leave the bombs in place. younger molten rock. Do you see any bombs with From here you can see two of the structural domes: glassy cores? The glassy cores were analyzed Red Bomb Crater. Pull into the short Return to your vehicle and continue west. Along Graben Dome (10:30 to 12 o’clock) and South Dome and appeared to have re-melted 17,000 years ago, parking loop road. Avoid getting stuck by the skyline you can see Ruptured Raven Ridge (1 (9:30 to 10:30). Between here and the next stop, note suggesting that this cinder cone is that old. Please do staying on the firmly packed surface. More o’clock), part of the original domal arch of Central the small bread-loaf shaped domes that are small- not break open or collect the bombs. than one vehicle has sunk to the hubs in Dome. scale versions of the larger domes. this tephra. If you want to see the graben in Graben Dome, park Between Red Bomb Crater and East Twin Crater Park at the edge of the road where you here and hike up. Please, no vehicles. Even four- While you stand on the crater rim and look toward the on West Dome, Stop Number 8, you will come upon can see lava flows to either side. You wheel drive vehicles will damage the area. southern skyline, Steens mountain (7:30) rises nearly several dead-end roads. Keep right on the main, well- are looking at a scene of both quiet and a mile above the Blitzen Valley. It is a west sloping traveled road until you come to three roads branching explosive basaltic eruptions. Continue westward. As you round Big Bomb Crater, fault block (6 to 9 o’clock) rising to an overall elevation off at about 2.4 miles. Take the middle branch. You at about 0.2 miles, you’ll see the Lava Pit Crater of 9,773 feet above sea level. should be able to see two large craters in the side Lava flows, or streams of molten rock, at Diamond Flow (10:30).