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Chapter 17: Streams and Floods: The Geology of Running Water

Geotours

Download Geotours.

Getting Started :

If you haven’t done it already, download Google Earth™ and install it on your computer.
If you haven’t done it already, download the Geotours.kmz file and save a copy to your desktop. (The Geotours.kmz file contains the Geotours for all chapters, so you only need to download this once!)
By downloading Geotours.kmz you acknowledge that it was created solely to accompany Steve Marshak's Earth: Portrait of a Planet and Essentials of Geology and is limited to use with only Steve Marshak's Earth: Portrait of a Planet and Essentials of Geology and may not be reproduced, stored in a retrieval system, or transmitted in any form by any means for any other purpose without the written permission of the publisher.
Double-click the Geotours.kmz file and Google Earth™ will open automatically.
In the left-hand sidebar you will see a Places menu, and in the Temporary Places folder you will see an EARTH_3e.kmz file. Double-click the file and you will see a list of Geotours for each chapter.
Then open the Geotour folder you want to explore! If you’d like to read more about the features of Geotours see Using Geotours, or go to our Helpful Resources section.

STOPS ON GEOTOUR 17: Fluvial Landscapes

Deep Gorge in the Himalayas
Headward Erosion, Canyonlands National Park, Utah

See also Worksheet Problem 1
"What a Geologist Sees" Geofeatures: Three Points of Headward Erosion, Entrenched Colorado River, Moenkopi Formation, White Rim Sandstone, and Cutler Formation

Meanders along Rio Ucayali, Peru

See also Worksheet Problem 2

Incised Meanders, Canyonlands National Park, Utah

See also Worksheet Problem 3

Mid-Stream Bars, Rio Negro, Brazil
Point Bars, Trinity River, Texas

See also Worksheet Problems 4-5

Trellis Drainage Pattern, Pennsylvania

See also Worksheet Problem 6; Problem Bonus: Water: Jacks Creek, Meadow Creek, and fifteen other Creeks

Radial Drainage, Mt. Shasta, California
Dendritic Drainage, Pennsylvania

GEOTOUR 17 WORKSHEET

Streams stand out in the landscape, for they carve intricate shapes as their waters flow from high areas to low. In this Geotour, we visit a variety of landscapes whose features are a consequence of deposition and erosion in a fluvial setting.

Headward Erosion, Canyonlands National Park, Utah
1. Double click in Image G17.2–3, then, open the WAGS folder and double-click and check the box next to the placemarks labeled “Point of Headward Erosion.” In this view from Grand View Point in Canyonlands National Park, three stream branches labeled with placemarks are experiencing headward erosion. Headward erosion allows streams to lengthen in the upstream direction. As seen from this viewpoint, in which direction (right or left) are the streams lengthening?

Meanders along Rio Ucayali, Peru
2. The placemarks for Problem 2a, b, and c highlight several features associated with low-gradient, meandering streams. Match the appropriate placemark with the following features:
• point bar
• ox-bow lake
• abandoned point bars

Incised Meanders, Canyonlands National Park, Utah
3. Click on Image G17.5 to see a meandering river flowing at the floor of a steep-walled canyon in Canyonlands National Park.

(a) What will happen in the future when the two meander necks visible in this image are breached (cut through)? (Note: You can see an example of where a meander neck has been breached, causing the meander to be abandoned, about 36 km NNE of the Image G17.5 placemark.)

(Note: You can see an example of where a meander neck has been breached, causing the meander to be abandoned, about 36 km NNE of the Image G17.5 placemark.)

(b) Reorient the image so that you are looking straight down. What is the depth of the canyon in which the stream at this site is now flowing?

To cause the incisement observed, what is the minimum change in elevation of the river’s base level, relative to this site?

Did the base level rise or sink relative to this site?

Point Bars, Trinity River, Texas
4. The placemarks for Problem 4a, b, c, and d highlight several features associated with low-gradient, meandering streams. Match the following with the appropriate placemark:

• point bar
• cutbank
• ox-bow lake
• yazoo tributary

Note: Search the area and you can also find examples of meander necks, recently breached meander necks, and abandoned meanders.

5. Surveyors sometimes use the course of a stream to define political boundaries (e.g., county lines, state lines). Would a meandering stream like the Trinity River make a good permanent boundary? Why or why not?

Trellis Drainage Pattern, Pennsylvania
6. Double-click on the Problem 6 folder, and check the folder box. The placemarks for Problem 6c will appear, as well as a network of blue lines that mark the courses of streams in a region about 51 km WSW of the placemark for Image G17.9. Zoom into the highlighted area. Jacks Creek is the stream with the thickest blue line.

(a) What is the overall compass bearing (trend) of Jacks Creek, and how does it compare to the trend of the nearby forested ridges?

(b) In which direction is Jacks Creek flowing? (Hint: Zoom out until you find where Jacks Creek empties into a larger river.)

(Note: If you look closely at the shape of the ridge at the end of Jacks Creek, you can see that the ridge is a plunging anticline.)

(c) Although the regional network of streams in the Appalachian Valley and Ridge Province is a trellis pattern, other patterns may develop locally. Note the angle at which the tributaries labeled by the placemarks for Problem 6c intersect other streams, and note the angle of bends in these streams. What is this angle, and thus what is the local drainage network pattern defined by the blue-highlighted streams?

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StudySpace: Chemistry 2e.