Name That Volcano: Orr Lake
A Note of Encouragement:
Welcome to the Klamath National Forest Earth Cache program! Most of the Earth Cache locations are located away from established recreational trails and roads. Visitors are strongly encouraged to check with Ranger District offices for information on current road and trail conditions before visiting sites, and be prepared for cross-country hiking.
Layered clothing, water, and appropriate maps are essentials when traversing the remote, rugged landscape of the Klamath National Forest. Please be aware of wildlife and poison oak while visiting Earth Cache locations in the forest and use caution when traveling down narrow winding forest roads.
Location Information: UTM 10 T 0584139 4612868
Orr Lake campground is located in the Goosenest ranger district of the Klamath National forest. The EarthCache site is at the boat launch facilities on the lower portion of the campground. You will need to go to the GPS coordinates in order to answer the logging questions. The campground is off county road 8Q01 near the town of Bray.
You can still access this location during the winter (pending weather conditions); however, the campground facilities are closed.
Geological Information:
The Cascade Mountains are the result of numerous volcanoes and volcanic eruptions. These volcanoes range in size, type, and activity. Some of the Cascade volcanoes in the Klamath National Forest (KNF) are still active. Even in their dormant state, the evidence of their activity is seen throughout the forest, and their massive silent bodies still provoke awe.
The volcanoes that make up the Cascade Mountain range are very young when you consider the age of the Earth, 4.6
billion years. These volcanoes are less than 2
million years old, and the highest peaks are even younger (less than 100,000 years old). Despite their young age, the Cascade volcanoes significantly define the surrounding landscape whether it is the volcanoes themselves or the destruction caused by their eruptions.
In the Cascades Mountain range you can see various types of volcanoes, shield, stratovolcanoes, cinder cones, lava domes, etc. This Earth Cache focuses on 2 of the most recognizable volcanoes, shield and stratovolcano. Identifying volcanoes can give you a better understanding of their relationship to the surrounding landscapes.
Shield volcanoes are very large horizontally but have very shallow slopes (not very tall relative to their width). For example, Hawaii’s Mauna Loa is the
largest shield volcano on Earth in terms of area (Figure 1). Shield volcanoes have low viscosity lava, which means the lava moves more fluidly or easily. The fluid lava cools very slowly allowing it to travel further, which accounts for the large size and shallow slopes of shield volcanoes. Low viscosity lava eruptions are not usually explosive because the lava is low in volatiles (water and silica). Shield volcano eruptions are less dangerous than stratovolcanoes, but they significantly modify and shape the landscape. The effect of shield volcanoes can easily be overlooked since most people do not notice they are there mistaking them for a simple hill.
Stratovolcanoes, also known as composite, are cone shaped consisting of alternating layers of lava and volcanic material. Unlike shield volcanoes, stratovolcanoes are usually steep sided due to the high viscosity lava (Figure 2). The higher viscosity lava cools quickly, causing it to harden before it travels very far. Stratovolcanoes are known for explosive eruptions, like the 1980 Mt. St. Helens catastrophic eruption. Explosive eruptions are caused by high amounts of volatiles in the lava. Think about what happens when you open a soda after it has been shaken; the contents go everywhere. Like a shaken soda, the contents of a volcano during an explosive eruption are distributed throughout the landscape. Stratovolcanoes are more noticeable in terms of appearance and eruptions, but the effect they have on the
landscape is much different than shield volcanoes. They are sudden events that change the volcano’s appearance and destroy anything around it like forests. While stratovolcanoes cause relatively short term destruction, shield volcanoes quietly modify the landscape. When active they can continuously deposit material, while stratovolcanoes may have one dangerous eruption every several hundred years.
Orr Lake provides a scenic view of multiple volcanoes. Go to the coordinates and stand facing the southwest (see Figure 3). This will allow you to answer the logging requirements and questions below.
For further investigation into volcanoes and the area, please check out another KNF EarthCache, the Lifecycle of a Volcano: Hole in the Ground (
GC41A5G).
Logging Requirements and Questions:
- The text “GC44JGH” on the first line
- Number of People in group
- The date or season
- What type of volcano(es) do you see at points A and B (Figure 3)? Describe the volcano(es).
- Other than the volcanoes in Figure 3, what volcanic evidence can you find around Orr Lake? Do you see any other volcanoes or volcanic rocks? (Explore the campground!)
Contacts:
Goosenest Ranger District
37805 Highway 97
Macdoel, CA 96058
(530) 398-4391
FAX (530) 398-5749
TDD (530) 398-5744
Klamath National Forest
Supervisor's Office
1711 South Main Street
Yreka, CA 96097-9549
(530) 842-6131
FAX (530) 841-4571
TDD (530) 841-4573