Laboratory Manual for Introductory Geology 4e

GEOTOURS EXERCISE 13
Visualizing Dynamic Stream Landforms
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Exploring Geology Using Google Earth
1. Visit digital.wwnorton.com/geolabmanual4
2. Go to the Geotours tile to download Google Earth Pro and the accompanying
Geotours exercises file.
Expand the Geotour13 folder in Google
Earth by clicking the triangle to the left of the
folder icon. The folder contains placemarks
from three different locations that highlight
spectacular landforms associated with
streams.
(a) Check and double-click the Rio
Ucayali River, Peru placemark to fly
to a river in South America. Study
the time-lapse animation in the
placemark balloon to observe the rapid
changes in meanders that occurred
between 1984-2012. In addition to
migrating laterally and cutting off some
meander necks, do the meanders
migrate downstream or upstream?
(b) Check and double-click the GoosenecksSP_TopoMap overlay to fly to a section of the San Juan River near
Mexican Hat, UT. Given the extensive meanders and the closely spaced contours for the stream valley walls,
explain how these features likely evolved. Just for fun...check and double-click the Lake Powell placemark to fly
downstream (west) to where the San Juan River flows into the backwaters of Lake Powell (caused by the Glen Canyon
dam on the Colorado River) to see what human induced changes to base level have caused.
(c) Check and double-click the Cumberland_TopoMap overlay to fly to the Cumberland, MD area. Braddock
Run used to follow approximately along the Interstate 68 path across Haystack Mountain to flow into the North
Branch of the Potomac River (NBPR). (Check the Interstate 68 former Braddock Run and Haystack Mountain
placemarks.) Now that path is a wind gap through the mountain, and Braddock Run flows to the river at Eckhart
Junction (check the Eckhart Junction placemark). Given that Braddock Run originally had to erode down through
the resistant ridge of Haystack Mountain while another tributary of the NBPR (check to turn on Tributary path)
could headwardly erode along the less resistant shale valley, develop an explanation that created the wind gap and
altered Braddock Run’s direction of flow.
360 CHAPTER 13 LANDSCAPES FORMED BY STREAMS