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EarthCache

When Dinosaurs Roamed the Earth

Hidden : 5/30/2007
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

Dinosaur Rock, Lebanon County on State Game Lands 145;

The boulder area covers about an acre.


Geology: This outcrop is an erosional remant of an igneous rock called diabase. During the Jurassic period in southeastern Pennsylvania, a large mass of molten rock cut upward into Triassic sedimentary rocks. Subsequent erosion of rocks allowed these resistant rocks to form some of the highlands of the piedmont. The diabase is composed mostly of minerals plagioclase feldspar and pyroxene. Crystals of plagioclase are enclosed with pyroxene crystals, which give it a texture called "ophitic." The boulders are spheroidally weathered.

A profile of the rocks from the north or south reveals a form that gives the outcrop its name—"Dinosaur Rock."

The outcrop is said to date from the Triassic Period, 208-245 million years ago, when the first dinosaurs appeared on Earth.

Site is potentially threatened, especially by graffiti.

NO access from the PA turnpike, park at the State Gamelands 241 parking area just across the road from the trail to Dinosaur Rock. ( Here are the coords for the parking area across the road from "Dinosaur Rock... N40 13.780 W076 30.250)

Follow the trail about 500 feet to the diabase rocks. Easy walking though cars travel fast along Route 241, which must be crossed from the parking area. Path is fairly smooth and flat but may be rough for a wheelchair. Rocks may be slippery; climbing is not recommended.

TO CLAIM A "FIND", E-MAIL (DO NOT LIST ON THIS SITE) THE ANSWERS TO THE FOLLOWING 4 QUESTIONS.

1. What does the "ophitic" texture tell us?

2. What likely caused the spheroidally weathered boulders?

3. What is the heritage value of this site?

4. Estimate the height of the diabase remnant.

Additional Hints (No hints available.)



 

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Current Time:
Last Updated: on 11/15/2017 3:26:54 PM (UTC-08:00) Pacific Time (US & Canada) (11:26 PM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum

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