National Park Service U.S. Department of the Interior Zion National Park Weathering, Erosion, and Change Geologic Events in Zion PHOTO CREDIT Contents Introduction 2 Core Connections 2 Background 2 Activities Earth’s Power Punches 4 Rock On, Zion 5 It Happened Here! 6 Glossary 8 References 9 Introduction This guide contains background information about how weathering, erosion, and other geologic processes such as volcanoes continually shape the landscape, and directions for three activities that will help students better understand how these processes are at work in Utah. This guide is specifically designed for fifth grade classrooms, but the activities can be NPS modified for students at other levels. Theme of deposition (sedimentation), lithification, The Earth’s surface is a dynamic system that is uplift, weathering, erosion, tectonics, and constantly changing due to weathering, volcanic activity make the park a showcase for erosion, floods, earthquakes, volcanoes, and changing landscapes. other geologic events. Deposition (Sedimentation) Focus Zion National Park was a relatively flat basin The activities focus on relationship between near sea level 275 million years ago, near the NPS/MARC NEIDIG geologic processes such as weathering and coast of Pangaea, the land area believed to erosion and changes on the Earth’s surface. have once connected nearly all of the earth’s landmasses together. As sands, gravels, and Activities muds eroded from surrounding mountains, Earth’s Power Punches streams carried these materials into the Students view a presentation of digital im- basin and deposited them in layers. The sheer ages showing the forces that shape the Earth’s weight of these accumulated layers caused surface. Then students view images from Zion the basin to sink, so that the top surface and determine which geologic forces have always remained near sea level. As the land contributed to the landscapes shown. rose and fell and as the climate changed, the NPS/CAITLIN CECI depositional environment fluctuated from Weathering and erosion are shallow seas to coastal plains to a massive some of the Earth processes that Rock On, Zion shape the geology and scenery desert of windblown sand. This process of Students will learn how Zion was formed and in Zion National Park. sedimentation continued until over 10,000 evaluate how weathering and erosion contrib- feet of material accumulated. uted to the formation of the rock layers and subsequent carving of the canyon. Core Connections Lithification Mineral-laden waters slowly filtered Utah Core Curriculum It Happened Here! through the compacted sediments. Fifth Grade Science Students draw on the knowledge they have Iron oxide, calcium carbonate, and silica Standard 2: Students will gained about geologic events to invent a spe- acted as cementing agents, and with pressure understand that volcanoes, cific event and imagine themselves in it. from overlying layers over long periods of earthquakes, uplift, time, transformed the deposits into stone. weathering, and erosion reshape Earth’s surface. Ancient seabeds became limestone; mud and Background clay became mudstones and shale; and river sand and sand dunes became sandstone. Each Objective 1: Describe how Zion National Park is located along the edge weathering and erosion layer originated from a distinct source and so of a region called the Colorado Plateau. Uplift, change Earth’s surface. differs in thickness, mineral content, color, tilting, and the erosion of rock layers formed and eroded appearance. Objective 2: Explain how a feature called the Grand Staircase, a series volcanoes, earthquakes, and of colorful cliffs stretching between Bryce uplift affect Earth’s surface. Tectonics and Uplift Canyon, Zion, and the Grand Canyon. In an area from Zion to the Rocky Mountains, Objective 3: Relate the building tectonic forces deep within the Earth up and breaking down of Zion has spectacular geology. The arid climate pushed the surface up creating the Colorado Earth’s surface over time to the and sparse vegetation expose bare rock and various physical land features. Plateau. This was not chaotic uplift, but reveal the park’s geologic history. Evidence Zion National Park, 2015 Erosion, Weathering, and Change 2 slow vertical hoisting of huge blocks of the The Virgin River is still excavating. Upstream crust. Zion’s elevation rose from near sea level from the Temple of Sinawava, in The Narrows, to as high as 10,000 feet above sea level. the river cuts through Navajo Sandstone, Uplift is still occurring. creating a slot canyon. At the Temple of Sinawava, the river has reached the softer For many millions of years, portions of the Kayenta Formation below. Water erodes the Pacific Plate (oceanic crust) subducted shale, undermining the overlaying sandstone beneath the thicker, more buoyant North and causing it to collapse, widening the American Plate (continental crust). This canyon. As the plateaus continue to rise, the subduction formed mountains and volcanoes basins drop, and the river cuts, Zion Canyon along the west coast, and led to the formation is expanding upstream at a rate of about 10 of the Rocky Mountains. Later, changes in miles of lateral movement every million years. plate geometry led to the end of subduction along much of the West Coast (although Volcanic Activity subduction continues today in the Pacific Volcanic vents, created as a result of the Northwest). Instead of being pushed together, weakening of the Earth’s crust during tectonic the plates began to slide sideways (lateral events, allowed lava flows and cinder cones to motion), as is seen today in California’s form. Cinder was piled several hundred feet San Andreas Fault. This lateral motion high in classic cone shapes and lava flowed stretched portions of western North America; into valleys. Cinder cones and black basalt creating a region called the Basin and Range. flows are visible west of Rockville and on the Westernmost Utah is part of the eastern Kolob Terrace. edge of the Basin and Range province, where stretching continues today along active Fractures and Faults faults like the Hurricane and Wasatch Faults. Fractures and their control of canyon erosion Despite the mountain building and stretching are one of the most striking features of the that canyons of the Virgin River. The fractures (not occurred in the surrounding areas, the faults because there is no displacement) exert Colorado Plateau rose to its high elevation a strong influence on the erosion of smaller with little deformation. canyons in the Navajo Sandstone. Erosion These fractures are believed to have formed The uplift of the Colorado Plateau gave the due to tectonic compression and extension streams greater cutting force in their descent forces. The fractures form perpendicular to to the sea. The park’s location on the the direction of the compression and western edge of this uplift caused the streams extension. The dominant fracture direction to tumble off the plateau, flowing rapidly in Zion is roughly north-south. There are also down a steep gradient. These streams began fracture sets that are east-west (Kolob eroding and cutting into the rock layers, Canyons) and northeast–southwest (Kolob forming deep and narrow canyons. Terrace and Hop Valley). Grain by grain, the Virgin River has carried While the straight north-south canyons away several thousand feet of rock that once on either side of Checkerboard Mesa are lay above the highest layers visible today. On controlled by large fractures, the criss-cross average, the Virgin River transports one fractures on its surface are of a more million tons of sediment per year. The rate recent origin. The horizontal banding is the varies dramatically with the flow of the river, result of differential weathering of the with the vast majority of sediment transport crossbedded sandstone, while the vertical occurring during floods. When the river is low cracks are thought to be the result of freeze/ and clear, very little sediment is moving, and thaw cycles at the surface of the rock. much of the transport involves minerals dissolved in the water. Zion National Park, 2015 Erosion, Weathering, and Change 3 Earth’s Power Punches Suggested Procedures 1. Show the Utah State Geological Survey Duration Landscapes presentation and use 1 hour accompanying notes for each slide to introduce students to the variety of Location geologic processes that occur to shape the Indoors Earth. 2. Show each of the Zion landscape images Key Vocabulary and ask the students to name which Earth blind arch, butte, cinder cone, erosion, process they think was at work to create the earthquake, geologic processes, mesa, rock landscape in each image. Have the students layers, uplift, volcanoes, weathering write down a list of Earth changing processes for two or three of the images. Objectives By the end of the activity, students will be able 3. Ask the students to determine which to a) name three Earth processes that shape processes can occur quickly (minutes/ the landscape, b) name two Earth processes hours) and which occur over a long that have helped to change the landscape at period of time (years to millions of years). Zion, c) name which Earth processes have Have students discuss their results with occurred quickly and which have occurred the class and describe the processes they slowly. investigated. Ask the students to describe how they came up with their determination Method of the time it took for each process to Students view a presentation showing occur. geologic processes that contribute to changing landscapes. Applying their knowledge to Zion, students view images and identify evidence of geologic forces such as weathering, erosion, earthquakes, volcanoes, and uplift. Background The Earth’s surface constantly changes due to weathering, erosion, earthquakes, volcanoes, and uplift. At Zion National Park evidence of these processes is observed in the water and wind carved rocks, uplifted geologic layers, volcanic flows, cinder cones, mesas, blind arches, and other landforms.