W. W. Norton Home  |   Help  |   Contact Us  |  Site map  |  Site Credits Colorblind Mode: On • Off

Chapter 4

Chapter 4: Up from the Inferno: Magma and Igneous Rocks

Geotours

Download AnthroTours

Using the power of Google Earth, GeoTours take you on flyovers of key locations discussed in the text.

StudySpace student website and ebook icons in each GeoTour connect your to the text and online review materials.

Dialogue boxes accompanying each site include text, figures, photos.

Download GeoTours.

System Requirements for Google Earth™

Getting Started :

Geotour 4: Exposures of Igneous Rocks

Batholiths and Laccoliths
1a. Yosemite National Park provides spectacular glaciated exposures of the Sierra Nevada batholith. The batholith is comprised of many separate plutons, which intruded into the area as part of a Mesozoic-age subduction system.

Check and double-click the placemark for Problem 1a to fly to the spectacular Half Dome in Yosemite National Park. Given that it is part of a batholith, what type of rock texture would you expect to see at Half Dome?
1b. Visitors commonly note the rounded appearance of the back side of Half Dome. It was not polished by glaciers, but rather fractured off in sheets much like how one might peel layers from an onion. This process occurs because these rocks formed at ~20-25 km depth, but have experienced a removal of confining pressure since they are now exposed at the surface (think of how a sponge expands once you remove your hands pressing down on it). What is this process called? (Hint: Look these words up in your glossary).
1c. Check and double-click on the North America Batholiths map in the folder labeled Problem 1. You will see the exposed batholiths of the western United States. Using the transparency slider at the bottom of the Places panel, you can make the overlay transparent. To get a sense of the size of the Sierra Nevada batholith, determine its length between placemarks for Problem 1c using the Measuring Tool (in km).
1d. Check and double-click on the red polygon for the Henry Mountains laccolith complex in the folder labeled Problem 1. This complex consists of many blister-like intrusions. Note the size difference between this intrusion and the Sierra Nevada batholith. Estimate how much smaller in length the Henry Mountains laccolith complex is relative to the batholith.
1e. Double-click on the placemark for Problem 1e to zoom down to the south flank of the Mt. Hillers laccolith. The laccolith is comprised of gray andesite that has intruded into Mesozoicage sedimentary rocks and upturned them on the flanks of the intrusion (recall that laccoliths are concordant intrusions that cause the overlying sedimentary layers to fold up in a blister or mushroom-shaped pattern). The sedimentary rocks over the intrusion have been eroded. Placemark Problem 1e highlights a tabular intrusion from the main laccolith that is parallel to the upturned sedimentary layers. What kind of intrusion is this?

Dikes
2a. A dike is a tabular igneous intrusion that is discordant and cuts across pre-existing layering.

Check and double-click placemark Problem 2a. Which of the following statements is incorrect?
2b. Check and double-click the placemarks for Problems 2b-i, -ii, and -iii. These placemarks highlight radial dikes from the volcanic neck at Shiprock. Which of the following is the most reasonable explanation for this pattern?

Submit to Gradebook:

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

Print This Page
Bookmark and Share

In This Chapter

The Norton Gradebook

Instructors and students now have an easy way to track online quiz scores with the Norton Gradebook.

Go to the Norton Gradebook

Norton Ebooks

The ebook version offers the full content of the print version at half the price.

Norton Ebooks