Planetary Geology on Earth: Odessa or Mars? EarthCache
Hidden : 5/11/2013
Difficulty:
3.5 out of 5
Terrain:
3 out of 5

Size: Size: other (other)

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Geocache Description:

Odessa or Mars?

Who knew Odessa and Mars had so much in common? Well, maybe some folks thought so, but they probably didn't know the real reason. Basaltic ring dike structures, called the Odessa Craters, are found in the Odessa area, but nowhere else on Earth. However, they are found on Mars!
Are you kidding me?
Craters like this are found only on Mars and around Odessa. How neat is that?


Odessa Craters
"Amphitheater Crater", as seen from an aerial photo, is one of several basaltic ring dike structures in the Odessa area. The basaltic ring dike (the outer basalt wall) found at this crater is about 50 feet higher than the bottom of the pit and the crater is about 700 feet wide. The gray lines on the right side of the photo are roads.

In the Odessa area, erosion by Ice Age Floods has exposed unusual basaltic ring dike structures. The unusual features appear as circular structures or craters in the basalt. Dozens of them are found in the nearby and surrounding area. They are defined by arcuate (bow shaped) concentric basalt ridges that surround hills, mesas, or crater-like depressions. These quasi-circular basalt ridges range in size from 150 to 1500 feet in diameter. They vary from circular to elliptical concentric rings of low ridges separated by shallow swales. They are only known to exist in a limited area of the Columbia Basin Scablands uncovered by the Lake Missoula flood some 15,000 years ago. However, similar structures were carved out of similar lava flows by comparable massive flood(s) on Mars.

Aerial photographs above: (a.) is from an area near Sprague Lake along I-90. Aerial photograph (b.) shows similar features of comparable size on the planet Mars.


Hmmm....This is very interesting.


Map of Odessa, WA area. Circles indicate basaltic ring dike structures. Many are on private land. Access to craters are permissible only on BLM Land.


Formation
There are a couple of theories for the formation of the basaltic ring dike craters. A primary theory is called the Lava and Water Interaction Model (Illustrated Below): Huge outpourings of basalt disrupted drainages causing local groundwater table to rise and intersect the confined, cooling lava. Among the results of this interaction was the development of doming and cracking of the overlying cooler basalts. Molten lava could have intruded fractures in the cooled crust leading to dike formation.


The basalt ring dike structures form like a dome or the rings in half an onion. Instead of cooling away from cooling surfaces above and below the lava flow, it cooled from a point at the base of the basalt flow; probably over a spring. As the basalt cooled and crystalized it shrank forming the colonnade and entablature. The cooling formed shrinkage cracks in the flow above the springs which would form a dome like structure. Later on when the Ice Age Floods eroded the Scablands the ring structures were left, some as domes and some as craters.



What do we know about the basaltic ring dike structures?

-They can best be seen from the air.
-Circular to ellipical in shape, often with 2-5 concentric ridges.
-Centers may be depressions or may be buttes.
-When depressions, may contain a pond or lake.
-Range in size from 150-1500 feet in diameter.
-Seen only on scabland surfaces.
-Typically form in an over-thickened type of basalt.
-Centered on Odessa area but found nearly as far east as Sprague and as far north as the Upper Grand Coulee.

Head this way to log this EarthCache!

The EarthCache coordinates are the main focus of this earth cache. At this location you will find the center or bottom of the Amphitheater Crater. To log this EarthCache you will visit the following craters: Wild Garden Crater, Amphitheater Crater, Cinnamon Roll Crater and Cache Crater.

Park at the parking lot on Washington State Route 21 at Waypoint P1, Odessa Crater Loop Trail Parking. Follow the 1.5 mile BLM loop trail going north/northeast on the marked trail. As you come down the trail at Waypoint S1, Wild Garden Crater View Point, you will see the center of the Wild Garden Crater.

1) Describe the soil composition and/or vegetation in the bottom of the crater.

Continue on the trail to the coordinates listed above for the earth cache at the center of the Amphitheater Crater.

2) As you enter the crater you can view the basaltic ring dikes. How many do you see? Describe the bottom of this crater including soil composition and vegetation. Compare this with the Wild Garden Crater that you observed earlier? Is it different or the same? Why might this be so?

Continue on the marked loop trail back to the parking area. When you arrive back at your vehicle proceed south on Highway 21 and turn left on Trejbal Back Road and proceed to Waypoint P2, Cinnamon Roll Crater Roadside Parking, to view the Cinnamon Roll Crater.

3) From this site on the side of the road what one thing stands out that is different from the two previous craters?

Return to Washington State Route 21 and head north. On the side of the road there is a parking area at Waypoint P3, Cache Crater Parking. Follow the walking trail to the observation area for the center of Cache Crater.

4) Describe the shape of the basalt walls on the west side of the crater (the side nearest the viewing area). How is this the same or different from the ring dikes that you observed in the other craters.

BLM map of Odessa Craters Trail. Circles indicate basaltic ring dike structures.

Email your answers to me before you log your visit. Feel free to post photos but be careful to not post pics that give away answers to the questions. We hope you have enjoyed learning about the basalt ring dike structures in Eastern Washington. Permission has been granted by the Bureau of Land Management (BLM) for this earthcache.

Note: During certain times of the year there could be snakes present. Please be cautious.

Congratulations to kiekefretter for FTF honors.
And Honorable Mention to J and T of Marin 5 for being a close Second To Find.

Additional Hints (No hints available.)



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