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Chapter 12: Deep Time: How Old Is Old?
Animations
Click on the links below to view animations created specifically for Earth: Portrait of a Planet. Animations require Macromedia's Flash Plug-in.
ANIMATION: Geologic History
A cross-section through the earth reveals the variety of geologic features. View 1 of this animation identifies a variety of geologic features; View 2 animates the sequence of events that produced these features, and demonstrates how geologists apply established principles to deduce geologic history. For more information, see Section 12.4 Principles for Defining Relative Age starting on p.418 and Figure 12.5 in your textbook.
WHAT A GEOLOGIST SEES: Unconformity
The photo shows the Siccar Point unconformity in Scotland, on the coast about 60 km east of Edinburgh; the sketch shows a geologist's interpretation of the unconformity. For more information, see Section 12.5 Unconformities: Gaps in the Record starting on p.423 and Figure 12.8 in your textbook.
ANIMATION: Types of Unconformity
This animation shows the stages in the development of three main types of unconformity in cross-section, and explains how an incomplete succession of strata provides a record of Earth history. View 1 shows a disconformity, View 2 shows a nonconformity and View 3 shows an angular unconformity. For more information, see Section 12.5 Unconformities: Gaps in the Record starting on p.423 and Figure 12.9 in your textbook.
Zoomable Art: The Record in Rocks: Reconstructing Geologic History
When geologists examine a sequence of rocks exposed on a cliff, they see a record of Earth history that can be interpreted by applying the basic principles of geology, searching for fossils, and using radiometric dating. For more information, see the Featured Painting on pp.426-427 in your textbook.
