Sibley Volcanic Regional Preserve Exploration As sure as the earth moves in Berkeley, there's a volcano just off Skyline Boulevard. Not just any volcano. This one's laying on its side with its guts exposed. At Sibley Regional Volcanic Preserve, you'll find the rocky body and layered underpinnings of one of the largest volcanoes that once dotted our geologic neighborhood. normal point_0 highlight highlight_point_0 normal point_1 highlight highlight_point_1 normal point_2 highlight highlight_point_2 normal point_3 highlight highlight_point_3 normal point_4 highlight highlight_point_4 normal point_5 highlight highlight_point_5 normal point_6 highlight highlight_point_6 normal point_7 highlight highlight_point_7 normal point_8 highlight highlight_point_8 normal point_9 highlight highlight_point_9 normal point_10 highlight highlight_point_10 normal point_11 highlight highlight_point_11 normal point_12 highlight highlight_point_12 normal point_13 highlight highlight_point_13 normal point_14 highlight highlight_point_14 normal point_15 highlight highlight_point_15 normal point_16 highlight highlight_point_16 normal point_17 highlight highlight_point_17 normal point_18 highlight highlight_point_18 normal point_19 highlight highlight_point_19 Sibley Volcanic Regional Preserve Exploration <table width="500"><tr><td> Permalink: <a href="http://www.kqed.org/quest/exploration/sibley-volcanic-regional-preserve-exploration">http://www.kqed.org/quest/exploration/sibley-volcanic-regional-preserve-exploration</a> Difficulty: Moderate, Accessibile: No, Duration: 2.2 hrs <h2>Sibley Volcanic Regional Preserve</h2> This Exploration created in collaboration with the   <a href="http://www.exploratorium.edu"><img src="http://www.kqed.org/quest/files/explo_logo_black3.gif" border="0"></a> <iframe scrolling="no" src="http://www.kqed.org/quest/television/embed/web-extra-sibley-volcanic-regional-preserve" width="320" style="border: 0px;" height="217"></iframe>As sure as the earth moves in Oakland, there's a volcano just off Skyline Boulevard. Not just any volcano, mind you. This one's lying on its side with its guts exposed. You might not recognize it right away, owing to its reclining position and the grassy coat it's adopted. But among the shrubs and grasses at Sibley Volcanic Regional Preserve, you'll find the rocky body and underpinnings of one of the largest of a handful of volcanoes that once dotted our geologic neighborhood. Join us and naturalist Steve Edwards of the East Bay Regional Park District on our latest Bay Area science hike. <h3>Location</h3> 6800 Skyline Blvd, Oakland, CA 94611 (<a href="http://tinyurl.com/6lj4lr">Map</a>) Phone: 888-EBPARKS (888-327-2757), option 3, extension 4554 Open between 5 a.m. and 10 p.m. unless otherwise posted or permitted <a href="http://www.ebparks.org/parks/sibley">Download a trail map</a> and more about the park. Special thanks to Steve Edwards, Isa Polt-Jones and Rosemary Cameron of the <a href="http://www.ebparks.org">East Bay Regional Parks District</a> for their participation. Robin Marks contributed to this Exploration. </td></tr> #exploration -122.1956934,37.8503461,10000 37.8503461 -122.1956934 relativeToGround 0 1500 45 1 1a. Soil layers in the hillsides <a href="http://www.flickr.com/photos/kqedquest/2516286199"><img src="http://static.flickr.com/3211/2516286199_17f72bffd4_m.jpg"/></a> - Bands of green and brown on the hillsides near Sibley reveal layers of soils created by different geologic processes. Greener grass means clay-like soils that hold moisture. Water drains out faster from gravely soils, leaving the grass brown. #point_0_map -122.1956934,37.8503461 1b. How to make a volcano <a href="http://www.flickr.com/photos/kqedquest/2516284073"><img src="http://static.flickr.com/2249/2516284073_b277cb0a87_m.jpg"/></a> - Our guide, Steve Edwards, demonstrates how California's volcanoes came to be. When two of the earth's tectonic plates collide, the heavier one will sink under the other. As the heavier plate moves toward the hot core of the earth, minerals in it melt and become magma. This heated magma, less dense than the solid rock around it, forces its way to the surface, sometimes explosively. #point_0_map -122.1956934,37.8503461 1 2a. Lava feeder <a href="http://www.flickr.com/photos/kqedquest/2516286615"><img src="http://static.flickr.com/2080/2516286615_a9ee5d6ee0_m.jpg"/></a> - Sibley's central geologic feature is its volcano, Round Top. Over millions of years, the movements of tectonic plates have pushed Round Top over onto its side. In this spot, you are standing in what was the interior of the volcano. This black lava flowed up through a crack in the earth's crust, to fill Round Top's crater. #point_1_map -122.1953522,37.8500602 2c. Mysterious marker <a href="http://www.flickr.com/photos/kqedquest/2516286999"><img src="http://static.flickr.com/2185/2516286999_38d48c48b4_m.jpg"/></a> - A man-made plum in the breccia pudding. Anyone have any idea what this is, or why it has been attached to this rock? #point_1_map -122.1953522,37.8500602 2b. Plums in the pudding <a href="http://www.flickr.com/photos/kqedquest/2517109774"><img src="http://static.flickr.com/3021/2517109774_cbb7ec6134_m.jpg"/></a> - This plums-in-the-pudding formation is called breccia (pronounced BREH-chuh). It's the result of lava erupting from a volcanic vent, dragging with it chunks of rock it passes on the way. Hot lava coming up through Round Top broke itself up while solidifying, and ripped pieces of lighter-colored sandstone and bluish schist off ancient rocks thousands of feet below the surface as it made its way upward. #point_1_map -122.1953522,37.8500602 2d. Cutting corners <a href="http://www.flickr.com/photos/kqedquest/2516288021"><img src="http://static.flickr.com/3221/2516288021_7dd50cb022_m.jpg"/></a> - This rounded hump of rock is a victim of weathering. Imagine a block of volcanic rock, shrinking as it cools, forming cracks. Between those cracks are roughly cubic blocks of lava. Their exposed corners weather faster than the rest of the rock, leaving behind spherical blobs with layers peeling like onion skins. #point_1_map -122.1953522,37.8500602 2e. Onion skin layers <a href="http://www.flickr.com/photos/kqedquest/2517110250"><img src="http://static.flickr.com/3045/2517110250_b7e01618a5_m.jpg"/></a> - Onion skin layers in the weathering rock, close up. #point_1_map -122.1953522,37.8500602 2f. Lava lake <a href="http://www.flickr.com/photos/kqedquest/2516288463"><img src="http://static.flickr.com/3243/2516288463_37d0db8530_m.jpg"/></a> - This flow once formed a lake of lava that congealed inside Round Top's vent. Erupting magma had to go up through this lake, or along side of it and erupt out of the side of the mountain. #point_1_map -122.1953522,37.8500602 1 3a. Basalt cobblestones <a href="http://www.flickr.com/photos/kqedquest/2516288933"><img src="http://static.flickr.com/3083/2516288933_03a826878b_m.jpg"/></a> - The path out to the quarry resembles basalt cobblestone. The rocks here are the same as those that made up the lava lake at Round Top. Geologists think they might have broken into small pieces after an eruption emptied the lake, but left its hardened surface intact. The hard lava collapsed into the void left behind by the eruption, breaking into millions of pieces. #point_2_map -122.19544,37.851522 3b. Basalt <a href="http://www.flickr.com/photos/kqedquest/2516289151"><img src="http://static.flickr.com/3277/2516289151_d83a331fb6_m.jpg"/></a> - A chunk of basalt, the most common rock on the face of the earth. The brownish weathering rind hides the rock's gunmetal blue interior. #point_2_map -122.19544,37.851522 3c. Basalt <a href="http://www.flickr.com/photos/kqedquest/2517111350"><img src="http://static.flickr.com/3077/2517111350_051e520c92_m.jpg"/></a> - Bluish basalt, up close. #point_2_map -122.19544,37.851522 3d. Narrow-leaved Mule Ears (sunflowers) <a href="http://www.flickr.com/photos/kqedquest/2516289031"><img src="http://static.flickr.com/3219/2516289031_102678708d_m.jpg"/></a> - We were not too busy looking at rocks to stop and admire the local wildflowers. Wyethia angustifolia, commonly known as Narrow-leaved Mule Ears, were welcome oases of yellow dotting our walk. #point_2_map -122.19544,37.851522 1 4a. The Quarry <a href="http://www.flickr.com/photos/kqedquest/2517111526"><img src="http://static.flickr.com/3107/2517111526_418a95b196_m.jpg"/></a> - Sibley's volcano, pushed over on its side, has had a second life as a quarry dug by Kaiser Sand and Gravel. The quarry, which cut through the interior of the top part of the volcano, provided basalt used in making roads. #point_3_map -122.190703,37.852651 4b. Standing in the volcano <a href="http://www.flickr.com/photos/kqedquest/2517112264"><img src="http://static.flickr.com/3204/2517112264_33cd720709_m.jpg"/></a> - Ranger Steve Edwards points across Round Top's crater, now tipped on its side, to Mt. Diablo in the distance. "That's not a volcano," he says, noting that many people think it might be because of its shape. "Here in Sibley, we're standing in the volcano." #point_3_map -122.190703,37.852651 4c. Crater tipping <a href="http://www.flickr.com/photos/kqedquest/2516284483"><img src="http://static.flickr.com/2241/2516284483_bf107ba341_m.jpg"/></a> - Steve demonstrates the volcano's position in the past, and now. His hand is the volcano's caldera, the depression left in the top of a volcano after an eruption. Here, it's upright, as it was millions of years ago when Round Top was active. #point_3_map -122.190703,37.852651 4d. Crater tipping <a href="http://www.flickr.com/photos/kqedquest/2517107288"><img src="http://static.flickr.com/2158/2517107288_b079dabe9d_m.jpg"/></a> - The action begins; as tectonic plates in northern California slide past each other, the forces of their movements tilt the volcano. #point_3_map -122.190703,37.852651 4e. Sibley's Round Top volcano tipped <a href="http://www.flickr.com/photos/kqedquest/2517108048"><img src="http://static.flickr.com/2091/2517108048_742693f998_m.jpg"/></a> - Sibley's Round Top volcano as it's positioned now, tipped onto its side. #point_3_map -122.190703,37.852651 4f. Quarry Mazes <a href="http://www.flickr.com/photos/kqedquest/2517111790"><img src="http://static.flickr.com/3125/2517111790_e52b8e581b_m.jpg"/></a> - Over the years, several mazes have been made at the bottom of the quarry, and are regular destinations for park visitors. #point_3_map -122.190703,37.852651 4g. The cliffs of Sibley <a href="http://www.flickr.com/photos/kqedquest/2517111898"><img src="http://static.flickr.com/3129/2517111898_2b245f387e_m.jpg"/></a> - Watch your step and don't go beyond the fences or you may end up part of the quarry! #point_3_map -122.190703,37.852651 1 5a. Bake zone <a href="http://www.flickr.com/photos/kqedquest/2516292329"><img src="http://static.flickr.com/3234/2516292329_63b93ce398_m.jpg"/></a> - The red part of this basalt outcrop is called a bake zone. The basalt lava on the left may have still been hot and steaming when the lighter volcanic ash on its right landed on it. The steam coming from the basalt may have turned the lighter volcanic ash red. #point_4_map -122.197497,37.857089 5b. Bake zone <a href="http://www.flickr.com/photos/kqedquest/2516292713"><img src="http://static.flickr.com/3240/2516292713_68dde33552_m.jpg"/></a> - Bake zones can contain some dramatic features. After a rain, these red rock formations turn blood-red. The red results from oxidation of iron. #point_4_map -122.197497,37.857089 1 6a. North quarry pit <a href="http://www.flickr.com/photos/kqedquest/2517113782"><img src="http://static.flickr.com/2161/2517113782_15a2ce2716_m.jpg"/></a> - You're looking northerly at another quarry pit left by Kaiser, exposing layered basalt lava. #point_5_map -122.195254,37.856713 6b. Cooling Layers <a href="http://www.flickr.com/photos/kqedquest/2517113046"><img src="http://static.flickr.com/3019/2517113046_96aca4fcd3_m.jpg"/></a> - in a close up of the wall of the quarry, we see layers of basalt lava, nearly perpendicular to the original flow. These layers were caused by jointing as the lava cooled and shrank. #point_5_map -122.195254,37.856713 1 7a. Steamy lava holes <a href="http://www.flickr.com/photos/kqedquest/2516293253"><img src="http://static.flickr.com/2252/2516293253_e0b6077ffe_m.jpg"/></a> - Holes, or vesicles, lend a swiss-cheese texture to some of the lava. These pockets were formed when water in the lava escaped as steam while lava was cooling. #point_6_map -122.197778,37.8575 7b. Vesicles filled with minerals <a href="http://www.flickr.com/photos/kqedquest/2516293971"><img src="http://static.flickr.com/3045/2516293971_4cd1436d76_m.jpg"/></a> - Over time, many of the pockets in the rock were filled with minerals precipitated from ground water or volcanic fluids. The green fillings shown here are celadonite, a mineral related to micas. #point_6_map -122.197778,37.8575 7c. Vesicles filled with minerals <a href="http://www.flickr.com/photos/kqedquest/2517116646"><img src="http://static.flickr.com/2215/2517116646_e6cc0b247c_m.jpg"/></a> - The mineral-filled pockets have a characteristic almond shape that indicates which direction the lava was flowing. The thinner, pointy end leads in the direction away from the volcano. The white rock is opal or chalcedony. #point_6_map -122.197778,37.8575 7d. Rhyolite <a href="http://www.flickr.com/photos/kqedquest/2516292185"><img src="http://static.flickr.com/2180/2516292185_6262acfe55_m.jpg"/></a> - This yellowish rock, called rhyolite, is also a volcanic rock. But Round Top didn't contain the material this rhyolite is made of. Four miles north of Sibley is another vent that spewed forth rhyolite, about 9.8 million years ago. At that time, it was erupting beside Round Top. Fault motion subsequently moved it north to Berkeley. #point_6_map -122.197778,37.8575 1 8a. Basalt flow <a href="http://www.flickr.com/photos/kqedquest/2516295331"><img src="http://static.flickr.com/2401/2516295331_d711378e34_m.jpg"/></a> - This basalt flow, about 150 feet thick, stretches all the way to Highway 24 east of the Caldicott Tunnel on Highway 24. Unlike the lavas in Hawaii, Round Top's flows were thick and slow-moving, advancing about as fast as leisurely walk. #point_7_map -122.199444,37.859167 8b. Wall of lava <a href="http://www.flickr.com/photos/kqedquest/2517117434"><img src="http://static.flickr.com/2205/2517117434_bbbf7e8b77_m.jpg"/></a> - Like the volcano it came from, this lava flow has been tilted onto its side, and its current position helps us imagine the flow as it slowly marched across the landscape. Such creeping lava would have set all the land around it on fire, sending blocks of hot lava tumbling off of it, and consuming everything in its path--including intrepid rangers and reporters. #point_7_map -122.199444,37.859167 1 9a. Welded cinder <a href="http://www.flickr.com/photos/kqedquest/2516296191"><img src="http://static.flickr.com/3111/2516296191_a714d06802_m.jpg"/></a> - These textured red blobs are a rare formation called welded cinder. They were formed when basalt exploded out of Round Top in small hot, fragments that landed on each other and stuck together. Their "real" name also offers a good example of geologist jargon: rocks stuck together are "agglutinated," if the pieces stuck together are pebble sized, they're "lappili," and if those pebble-sized pieces are rounded, it's an "agglomerate." #point_8_map -122.199722,37.859722 9b. Welded cinder <a href="http://www.flickr.com/photos/kqedquest/2516295975"><img src="http://static.flickr.com/3094/2516295975_38907fc813_m.jpg"/></a> - Behold: a close-up of the rare and beautiful agglutinated lappili agglomerate. Or maybe let's stick with the name "welded cinder." #point_8_map -122.199722,37.859722 9c. Quartz vein in rock <a href="http://www.flickr.com/photos/kqedquest/2516296375"><img src="http://static.flickr.com/2390/2516296375_7c7073a4d2_m.jpg"/></a> - Interesting quartz vein. Or is it calcite... #point_8_map -122.199722,37.859722 1 10a. Petroglyph? <a href="http://www.flickr.com/photos/kqedquest/2517118814"><img src="http://static.flickr.com/2140/2517118814_78e69736e6_m.jpg"/></a> - Ranger Steve points to a spiral pecked into a stone that juts out from a ridge top. #point_9_map -122.200278,37.860278 10b. Profanoglyph <a href="http://www.flickr.com/photos/kqedquest/2517119008"><img src="http://static.flickr.com/2130/2517119008_4360b64ba4_m.jpg"/></a> - Alas, our guide tells us, upon closer inspection, it's clearly been chipped out with a steel chisel. So, unlike a petroglyph, which is sacred, this carving is declared a "profanoglyph." #point_9_map -122.200278,37.860278 #path 1 -122.19903,37.84695 -122.1991,37.84694 -122.19832,37.84787 -122.19841,37.84778 -122.19841,37.84789 -122.19826,37.84782 -122.19795,37.84805 -122.19765,37.84818 -122.1972,37.84826 -122.19661,37.84855 -122.19638,37.84874 -122.19646,37.84862 -122.19642,37.84859 -122.19588,37.84924 -122.19551,37.84982 -122.19532,37.84988 -122.19537,37.85019 -122.19544,37.85026 -122.19548,37.85043 -122.19569,37.85034 -122.19582,37.84974 -122.19589,37.84963 -122.19599,37.84968 -122.19605,37.85 -122.19606,37.85033 -122.19593,37.85056 -122.19584,37.85061 -122.19562,37.85085 -122.19556,37.85132 -122.19544,37.85174 -122.19541,37.85167 -122.19545,37.85153 -122.1955,37.85148 -122.1955,37.85153 -122.19543,37.85151 -122.19547,37.8515 -122.19546,37.85128 -122.19542,37.8515 -122.19548,37.85155 -122.19521,37.85201 -122.19486,37.85217 -122.19392,37.85245 -122.19285,37.85291 -122.19228,37.8534 -122.19224,37.85359 -122.19242,37.85394 -122.19234,37.85393 -122.19185,37.85357 -122.19159,37.85301 -122.19131,37.85277 -122.19117,37.85275 -122.19122,37.85269 -122.19117,37.85262 -122.19063,37.85262 -122.19064,37.85258 -122.19116,37.85255 -122.19108,37.85252 -122.19141,37.85274 -122.1917,37.85303 -122.19184,37.85341 -122.19199,37.8536 -122.19316,37.85439 -122.1941,37.85534 -122.19508,37.85605 -122.19514,37.85617 -122.19509,37.85637 -122.19497,37.85632 -122.1951,37.85653 -122.19555,37.857 -122.19572,37.8571 -122.19595,37.85705 -122.19637,37.85718 -122.19648,37.85736 -122.1964,37.85721 -122.19628,37.85722 -122.19618,37.85715 -122.19613,37.85717 -122.19577,37.85708 -122.19564,37.85709 -122.19512,37.8566 -122.19496,37.85633 -122.19489,37.85639 -122.19494,37.85641 -122.19494,37.85636 -122.1949,37.85637 -122.19493,37.85637 -122.19498,37.85645 -122.19492,37.85637 -122.1949,37.85643 -122.19492,37.85634 -122.19488,37.8563 -122.1951,37.85605 -122.19516,37.85603 -122.19617,37.85603 -122.19643,37.85618 -122.197,37.85687 -122.19724,37.85697 -122.19758,37.85704 -122.1984,37.85766 -122.19838,37.85771 -122.19856,37.85781 -122.19893,37.85779 -122.19951,37.85795 -122.1999,37.85827 -122.19993,37.85858 -122.19962,37.85911 -122.19951,37.85922 -122.19953,37.85926 -122.19969,37.85953 -122.19965,37.85956 -122.19972,37.85969 -122.19969,37.85969 -122.19977,37.85965 -122.19978,37.85971 -122.1999,37.85969 -122.20012,37.85995 -122.20024,37.86017 -122.20038,37.86028 -122.20039,37.86033 -122.19978,37.8603