Honors Earth/Space Science
Colorado’s Volcanoes & Igneous Landforms
Name________________________________
Period_____Date______________
Using the Geologic Map of Colorado, find and record the names or locations and ages of the following:
1. 3 Calderas
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2. 3 Volcanic necks with radial dike swarms
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3. 5 Plutons or Batholiths
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4. 4 Basalt Flows ___________________________________________________
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5. Name the region that has the most igneous rocks. Describe the age and composition of these
rocks. What significance does this region have in the economic development of the State of
Colorado?
Instructions
1. Acquire an EHS iPad with the “EarthObserver” App. Open EarthObserver.
2. Find Colorado and turn the iPad to Landscape orientation.
3. Click on the
at the bottom right corner. Select the “World” tab.
4. Scroll down and click on “Geologic Maps” and scroll all the way to the bottom and select “United States State
Maps”. The Geologic Map of Colorado should appear. It is a colorful map showing the distribution of different
types and ages of rocks.
5.
For Question 1: Finding Calderas (the image to the right is a map of the
Kilauea Caldera in Hawaii)
a. Find the area in Southwest Colorado that is dominated by
reds, pinks and oranges.
b. Zoom in enough so that the scale in the upper right read 20 km
c. Find circular structures in this area. Two of them are
surrounded by black lines (mapped faults). One is surrounded
by river valleys. All three are labeled with their names. Record
the names of these calderas and the rock type symbol. Use
the key and identify type and age of the rocks in the calderas
6.
For Question 2: Finding volcanic necks with radial dike swarms
a. Zoom back out so you can see the whole state (the scale
should read 100 km).
b. Find the south-central part of the state. There is a band of blue
that trends North-South.
c. Zoom into the area just east of that band of blue, enough so that
the scale reads 20 km.
d. There are three bright pink “blobs” that have red lines radiating
out from them. These are the “Volcanic Necks with Radiating Dike
Swarms”
e. Two of these are named peaks and one is not. List the names of
the two and the general location of the third relative to the town of
Walsenberg.
f. Identify the symbol for the rock type and use the key to identify
type and age of the rocks.
7.
For Question 3: Finding Batholiths
a. Zoom back out so you can see the whole state (the scale should read 100 km). Find Colorado Springs
near the center of the state.
b. Zoom into the area just west of Colorado Springs so that the scale reads 20 km. You will see a dark
reddish orange area (the symbol is Yp). Use the key and identify this rock type, age and name.
c. Zoom back out so you can see the whole state (the scale should read 100 km).
d. Find Boulder and zoom into the area just west of Boulder so that the scale reads 10 km. You will see a
lighter orange area (the symbol is Xg). Use the key and identify this rock type, age and name.
e. Zoom back out so you can see the whole state (the scale should read 100 km).
f. Find Gunnison (about 1/3 of the way from the west edge and 1/3 from the bottom of the map). Gunnison
is just north of the areas where you found the calderas. Zoom (scale should read 20 km) into the
Gunnison area and move the map so that Gunnison is in the SW corner of the iPad.
g. Find the light pink rocks with the symbol YXg. Use the key and identify this rock type, age and name.
8.
For Question 4: Finding Basalt Flows
a. Zoom back out so you can see the whole state (the scale should read 100 km).
b. Most of the basalt flows in the state are indicated by the symbol Tbb and are mapped as a dark red with
lighter orange dots. Use the key to find the range of ages of Colorado’s basalt flows, record this age
range.
c. Because young basalt flows are very resistant to erosion, they often form mesas or buttes. Name the
basalt capped mesas in the following places:
i. Southeastern Colorado
ii. South and southeast of Alamosa in south central Colorado
iii. All around Glenwood Springs
iv. East of Grand Junction