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Lecture 4 Alluvial fans
What is an alluvial fan? … a fan-shaped deposit of alluvium found where a stream flows out of a mountain onto flatter terrain.
Narrow outlet (valley or gorge) Radial spreading alluvial fan Fan apex An alluvial fan in Death Valley
Sediments become finer- grained Coarse, channelized debris An alluvial fan in Death Valley
Ok, back to alluvial fans….. The evolutionary stages of alluvial fans
Alluvial fans: Steeper gradient than “normal” river profiles, thus are often dominated by debris flow processes
Kosi megafan, northern India
Migrating fluvial channels
Debris flows Shear stress vs. strain So flow is plug like and ceases as it reaches shallower surface, hence the velocity diminishes Flows also stop as they thin or lose water
Losing water and velocity caused the debris flow to become more viscous and stop, creating a very steep front
Debris flow “channel” on a talus in eastern Sierra Nevada
A closer view Note the existence of the “levees”
The radial deposition of alluvial fan Active depositional lobe
Period of active deposition, massive floods and debris flows
Debris flow fan caused by typhoon, southern Taiwan, 2005
So, what will the stratigraphy look like?
Channels near apex of fan
And suspended load deposits on distal portions of the fan
Downslope fining of alluvial fan deposits
Facies relationships, a Devonian fan in Sweden, showing characteristic interfingering of depositional facies
Pleasant Valley, Nevada
Three small alluvial fans on Soda Lake Road Is there anything strange of these fans?
Yes! They are offset 6.5 m by the 1857 earthquake
Alluvial Fans By Tim Baker & Tom Coburn. Basic Definition: An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens following.
Streams (,rivers, brooks, creeks, etc.). Processes Erosion Deposition.
Rivers and Streams. River Systems A river or stream: any body of water flowing downhill in a well defined channel A river or stream: any body of water.
Landforms of the Fluvial System. Objectives Describe formation and characteristics of alluvial fans Examine landforms formed by fluvial erosion and deposition.
Stream Erosion & Deposition Chapter 6 sections 1 and 2.
Objectives Describe how surface water can move weathered materials. Explain how a stream carries its load. Describe how a floodplain develops. Surface.
Lab 8 Stream Processes. Channel Types Braided - steeper, large sediment supply Meandering - less steep, lower sediment supply.
GE Sedimentary processes and products Lecture 5. Alluvial fans and fan deltas Geoff Corner Department of Geology University of Tromsø 2006 Literature:
Alluvial Fan Environments Badwater Fan, Death Valley Mars.
Due Tuesday, May 31 st at beginning of class Go to and enter 101 in left navbar search field. On G101 web page, download Problem Set.
Velocity Gradient – rise over run Channel shape Channel roughness Discharge – amount of water flow per unit time, as discharge increases,
Rivers 11.1 – Zones in rivers From Miller’s Living in the Environment.
River Transportation and Deposition. Load Suspended load Dissolved load Bed load Capacity Competency Sec Page Deposition.
McKnight's Physical Geography Lectures Chapter 16 Fluvial Processes © 2014 Pearson Education, Inc. Original by Andrew Mercer Mississippi State University.
The hydrologic cycle. Running water Streamflow Two types of flow determined primarily by velocity –Laminar flow –Turbulent flow Factors that determine.
Stream Erosion and Transport Erosion: Hydraulic action – erosion caused by the movement of water against stream sediment Abrasion – erosion caused by particles.
Investigation 3 Go with the Flow. The Grand Canyon is one place where erosion has taken place on a grand scale. Geologists are still trying to figure.
2 pt 3 pt 4 pt 5 pt 1 pt 2 pt 3 pt 4 pt 5 pt 1 pt 2 pt 3 pt 4 pt 5 pt 1 pt 2 pt 3 pt 4 pt 5 pt 1 pt 2 pt 3 pt 4 pt 5 pt 1 pt Mountains, Maps and More Stream.
XII. Streams A.The Hydrologic Cycle (components and pathways) B.Stream Velocity (controls and results) C.Drainage Patterns and Landscape Features (results.
River Systems Section 3 Section 3: Stream Deposition Preview Key Ideas Deltas and Alluvial Fans Delta Floodplains Human Impacts on Flooding Flood Control.
Unit 2: Erosion and Deposition by Water. Erosion The movement of sediments and other materials from one place to another. The movement of sediments and.
RIVERS AND ASSOCIATED LANDFORMS. Geomorphology Study of surface features of the Earth, curved by river; wind or glacial action. Evolution and structure.
What makes Earth unique. Where is the water on our planet ?
Water covers 71% of Earth’s surface and is the dominant agent governing environmental processes. The rates of human usage of water outpace the natural.
Chapter 9 Hydrologic Hazards at the Earth’s Surface.
Stream and River Deposits Chapter 11 Section 2. The Ability to Erode Gradient: Measure of change in elevation over a certain distance Gradient: Measure.
You have learned how to interpret how landforms are the result of a combination of constructive and destructive forces such as deposition of sediment and.
Aim: To develop a knowledge and understanding of Rivers in the landscape By the end of the lesson I should know: New terminology for important parts of.
Class 25: Hydrology. Class updates: Reading: Section Today’s topics: Water on Earth Water transport Water and geology Class 25: Hydrology.
12 River Systems Eric Christiansen Geology 111.
River Systems Four types, braided, meandering, anastamosing and straight.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Exploring Geology Chapter 16 Rivers and Streams.
STREAMS & RIVERS Chapter 6. REVIEW…. The Water Cycle.
Erosion and Deposition Water Sculpting the Earth’s Surface.
The Hydrologic Cycle PARTS OF A STREAM Channel - path of river Bed - bottom Head - beginning/source Mouth - ending Gradient - steepness of.
Potholes are formed due to stream or river erosion which initiates by simple plucking out at the riverbed by hydraulic action. These are variously.
Rivers: Fluvial Processes Yukon and Charley Rivers.
Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding.
Chapter 16: Running Water. Hydrologic cycle The hydrologic cycle is a summary of the circulation of Earth’s water supply Processes involved in the hydrologic.
Chapter 10: Streams: Transport to the ocean 1.Hydrological cycle 2.Stream profile and erosion 3.Sediment transport and deposition 4.Meanders 5.Deltas.
Channel Networks The drainage basin, or watershed, is the surface around a channel that "sheds water and sediment into that channel" Streams that get their.
Rivers Almost half of the water that falls to the Earth’s surface eventually ends up in a stream or river (runoff), where it travels overland to the.
Streams Nancy A. Van Wagoner Acadia University Distribution of Earth's water n What are the percentages? -Oceans - Glaciers - Groundwater - Lakes and.
© 2011 Pearson Education, Inc. Running Water Earth, 10e - Chapter 16.
7. Bedforms in coarse-grained channels Step-pool units Cluster bedforms Riffle-pool sequences.
Section 13.1 Streams and Rivers. ____________ – a stream and all its tributaries ________ – a smaller stream that empties into a larger stream.
River Systems. Objective Students will describe factors that affect the erosive ability of a river and the evolution of a river system.
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