Organize

Learn

Connect

Instructors now have an easy way to collect students’ online quizzes with the Norton Gradebook without flooding their inboxes with e-mails.

Students can track their online quiz scores by setting up their own Student Gradebook.

Chapter 13: A Biography of Earth

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 13: Earth Has a History

Folds of the Canadian Shield

See also Worksheet Problem 1

Appalachian Mountains, Tennessee

See also Worksheet Problems 2-3
"What a Geologist Sees" Geofeatures: Pine Mountain Fault, Jacksboro Fault, and two Folds; Overlay: Geologic Map

Maroon Bells, Colorado
The Rocky Mountain Front, Colorado
Basin and Range Rift

See also Worksheet Problem 4

GEOTOUR 13 WORKSHEET

The Earth displays the record of a long and complex geologic history marked by the collision of continents, the rifting of crust, the building and eventual erosion of mountains, and the deposition of strata. Geologists can unravel the character and sequence of events in this history by studying accumulations of sedimentary rocks, the age and character of metamorphic and igneous rocks, and the geometry of geologic structures. Different geologic provinces display the consequences of different events. Thus, you can see the evidence of Earth's geologic history in its landscapes. The following sites provide examples from North America.

Folds of the Canadian Shield
1. Double click on the placemark for Problem 1 and you will fly to a region south of Ungava Bay in Québec. Here, layers of rock have been intensely folded (a linear region containing these folds is called a fold belt). The rocks that crop out in this fold belt are now metamorphic, but before metamorphism consisted of sedimentary strata deposited along a passive margin in Proterozoic time.

(a) What is the trend of fold hinges in this area?

(b) Zoom up to an elevation of 150 km. You can now see that the folded rocks comprise a distinct belt, whose overall trend is parallel to that of the folds. West of the belt the land surface is grayer, and doesn’t have such a distinct texture. The grayer area without distinct folds is part of the Superior Province, a large block of Archean-age crust consisting mostly of high-grade metamorphic rock. The contact between the fold belt and the Superior Province is a thrust fault. What is the distance between the placemark for Problem 1 and the contact, as measured perpendicular to the trends of fold hinges?

(c) Another block of Archean crust called the Nain Province lies to the east of the fold belt. With this configuration in mind, provide a hypothesis that explains the origin of the fold belt. (Hint: Think about tectonic processes that cause mountain building.)

(d) With the answer to Problem 1c in mind, one might expect that the fold belt was a region of high elevation and rugged relief when it formed in the Proterozoic. Compare the present-day topography of the Superior Province to that of the fold belt. Is the difference greater than 200 m, or less?

Why?

Appalachian Mountains, Tennessee
2. The placemark labeled Problem 2 takes you to a portion of the Appalachian Valley and Ridge. Due to Paleozoic folding and faulting, the layers were deformed, so bedding is now tilted. Subsequent erosion left NE-SW trending ridges of resistant rock.

(a) Here, SW-dipping faults transported older rocks up and to the NW on top of younger rocks. The faults dip to the SW. What kind of faults are these?

Compression (squeezing) during the collision of Africa with North America caused the folds and faults of this area to form. In which direction was the “push” causing the squeezing directed? (Hint: Think of the direction of push that would create wrinkles in a rug as you pushed it across a floor.)

(b) Reorient your view so you are looking straight down and zoom out to 100 km. Note that the pattern of ridges stops abruptly off to the NW of the placemark for Problem 2. NW of the westernmost ridge the land surface has a different character, with randomly oriented hills—here, the topography is due to erosion of flat-lying beds. How far, measured perpendicular to the trends of the folds, is the westernmost ridge from this placemark?

Propose a hypothesis to explain what this boundary represents.

3. The fault highlighted by the Problem 3 placemark is called a tear fault. Note the different character of hills on either side of the fault—linear ridges to the NW of the fault, random hills to the SW. This contrast resembles the contrast discussed in Problem 2b. It appears that strata to the SW of the fault are flat-lying and undeformed, whereas strata to the NE have been transported by thrust faults. What type of motion took place on the tear fault to accommodate this motion?

Basin and Range Rift
4. Match the placemarks labeled Problem 4a, b, c, and d with either a “basin” or a “range.”
• 4a
• 4b
• 4c
• 4d

First Name:
Last Name:
Your Email Address:
Your Professor's Email Address:

Print this Page « Return to Chapter 13 Study Plan

StudySpace: Chemistry 2e.