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Learn more about local geology An introduction to: Briscoe Geology Park in Ashland. Walk through three time walks to learn how the Earth has changed over the past 4.6 million years. A selection of over 100 colorful tiles, interpretive signs and a Geology of the Rogue Valley visitor booklet will help to explain how plant and animal life has evolved and how local geology fits into the bigger picture. Crater Rock Museum in Central Point. The Crater Rock Museum is owned and operated by the Roxy Ann Gem and Min- eral Society, Inc. It houses many collections of minerals, artifacts, fossils, agates, geodes, gems and much more. Contact: (541)664-6081 www.craterrock.com Upper and Lower Table Rocks near Medford. Hike to the top to view andesite lava flows that have capped softer sedimentary rocks. You will see an excellent view of the Rogue River and the rest of the Rogue Valley. Lithia Park in Ashland. Granite and diorite boulders that have eroded from the Mt. Ashland pluton can be seen all along Ashland Creek. Outcrop near the junc- tion of Oak Street and Eagle Mill Road in Ash- land. This is a good lo- cation to observe sand- stone and shale of the Hornbrook Formation. Emigrant Lake Waterslide area Sandstone and conglomerate of the Payne Cliffs Formation can be observed here. Check with Jackson County Parks about entry fees. Presented by: North Mountain Park Nature Center A division of the Ashland Parks and Recreation Department North Mountain Park Nature Center 620 N Mountain Ave ~ Ashland, OR 541.488.660628 www.northmountainpark.org Version 3: September 2011 Index Geology and Geologists agate 17,24 Mesozoic Era 8,9,10 Geology is the study of the earth’s rocks and the processes that affect them. Geologists study aggregate 20,21 metamorphic rock 4,5,10,12,13 the earth in many different ways. Some geologists locate new rock quarries and mineral andesite 14,15,17,24 mineral water 22 deposits, while others study rocks in an effort to locate energy reserves including gas, oil, Applegate Formation 12 mining 19,20 and coal. Another important area of study for today’s geologists is to locate and tap into asphalt 23 Mt. Ashland 12 groundwater and springs. Still other geologists study rocks in an effort to better predict basalt 5,11,15,17, 18, 21 Mt. McLoughlin 7,14 natural disasters including earthquakes, tsunamis, volcanic eruptions, landslides, and Bear Creek valley 7,10,11,12,14 Mt. Mazama 11 avalanches. Paleontologists study rocks (and fossils) in an effort to learn about the history Cascade Mountains 6, 7, 9,11,14 Mt. Shasta 7 of life on earth. In addition to the economic and scientific applications of geology, the study Cenozoic Era 8,9,10 North American Plate 6,7,11,12 of rocks, minerals and earth processes are of interest to lay people for a variety of reasons. chert 5,12,15,17 obsidian 5,18 Along with their unending variety, beauty, and usefulness, rocks help tell the story of our cinders 11,15,17 Pacific Plate 6,7 landscape. People can use this information to prevent catastrophic erosion and flooding, clay 5 Paleozoic Era 8,9,10, help identify economic resources, and help protect and incorporate interesting features in concrete 23 Payne Cliffs Formation 9,10,13,14 city planning. Rocks and their associated minerals have been, and will always be, an integral conglomerate 5,15,17 petrified wood 13,15 part of our culture, technology, and daily existence. Crater Lake 11 Pilot Rock 11,13 dacite 13,15 placer deposits 19 diorite 12,15,16 plate tectonics 4,5,6,7,10,11,12 fossil fuels 2 pumice 5,15,18 About this booklet fossils 2,9,10,13,15 quartzite 12,13,15,16 gabbro 16 rock art 19 This booklet is one piece of the North Mountain Park Nature Center’s interpretation of our local geologic disasters 2,7,11 rock cycle 4,5 natural and cultural history. The area represented by the term “local” includes the Rogue Valley geologic time 8 sandstone 5,12,13,15,17,18 of southwest Oregon, with an emphasis on the Ashland area. glass 16,20,21 sedimentary rock 5,10,12,14 gold 16,19,20 sediments 5,9,10,12 While every attempt has been made to ensure accuracy, this booklet is not meant to be a formal granite 5,12,15,16 shale 5,12,15 work but is rather to be used by educators and others seeking an introduction to the topic of Grizzly Peak 11,13 silica 13,20 local geology. t is hoped that readers of this booklet will be inspired to use this information to High Cascades 9,11,14 siltstone 15,17 help make decisions that will enhance the livability of the Hornbrook Formation 9,10,12 silt 5 Rogue Valley for both its people and its wildlife now and into igneous rock 4,5,11,12,13 slate 5,15 the future. jasper 15,17 Table Rocks 14 Juan de Fuca Plate 6,7 tsunamis 7 We invite any and all comments to this document, which Klamath Mountains 10,11,12,15,16 volcanoes 4,5,11 will be updated periodically in an effort to reflect the most lava 5,13 Western Cascades 9,11,13 accurate information available. limestone 5,12 lode deposit 19 Acknowledgements: This booklet was written and formatted magma 4,6,11 by a team consisting of North Mountain Park staff members marble 5,12,15,16 and volunteers. Artwork and extensive background material were contributed by local geologist Len Eisenberg. 2 27 Plants and Animals Need Rocks Too! Table of Contents In general, most plants grow by absorbing nutrients from the soil. Their ability to do this depends on the nature of the soil. Depending on its location, soil contains Types of Rocks and How They Form ........................................................................................ 4 some combination of sand, silt, clay, and organic matter. The makeup of a soil (soil texture) and its acidity (pH) determine the extent to which nutrients are available to plants. Soil texture affects how well Plate Tectonics ........................................................................................................................ 6 nutrients and water are retained in the soil. Clays and organic soils hold nutrients and Earth Time Walk ...................................................................................................................... 8 water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it. This condition is called leaching. Major Events of the Phanorozoic Eon ...................................................................................... 9 When nutrients leach out of the soil, they are not available for plants to use. An ideal soil con- Geologic History of the Rogue Valley ................................................................................... 10 tains equivalent portions of sand, silt, clay, and organic matter. Formations of the Rogue Valley ............................................................................................. 12 Animals also make use of rocks for a variety of pur- poses. Reptiles, like snakes and lizards, use rocks for Local Rock Types .................................................................................................................. 15 protection and also to warm their body temperature. The internal temperature of a reptile depends on the weather outside which is why you will often find Summary of Rocks and their Uses ........................................................................................... 16 them basking on a rock in the sun to soak up the heat. Likewise, turtles also utilize the tops of rocks to Local Uses of Rocks and Minerals ......................................................................................... 18 keep them warm. Bears, cougars, coyotes and many other larger mammals find protection in caves or dens made from rocks. These dens provide shelter Modern Uses of Rocks and Minerals ....................................................................................... 24 and protection for the animal, especially during the time they raise their young. Many birds, such as Plants and Animals Need Rocks Too! .................................................................................... 26 hawks, eagles, and owls, build their nests up high on rocky cliff walls to protect their chicks. The height makes it difficult for other animals to reach their nest. Rocks also provide camouflage. For example, a Index ...................................................................................................................................... 27 mouse’s fur helps it to blend in with the sand and pebbles. Learn More About Local Geology ........................................................................................... 28 Moles, ants, badgers, groundhogs and other burrowing animals build their underground homes and tunnels in dirt, which consists of small, weathered rocks. By living underground, they are protected from predators above ground. These underground homes often consist of many chambers, or rooms, each with a specific purpose, such as food storage, raising young, and even bathrooms. 26 3 The removal, transport, use and Types of Rocks and How They Form disposal of all of these rocks, minerals, and fossil fuels can cause Most people think of rocks as solid, non-living bodies that we find beneath our great damage to the environment feet. While they do originate from the hardened crust of the earth, they are not and so this is one of the areas static. Instead, they have multiple “lives,” including being buried, melted, ex- geologist are working on to try to truded from volcanoes, weathered and chemically changed over thousands and find more sustainable ways
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