The Hole in the Wall EarthCache

Between mile posts #30 & #31. This turnout overlooks a 1984 landslide that covered the road and temporarily dammed the Powder River.

Note: the roadside signs appear to be badly damaged. To log this cache, you will need to include yourself and the current signs in your log, the educational details can now be found in additional photos on this cache listing.

Northeastern Oregon is a land where geologic history looms large. From the depths of Hells Canyon to the ridges of the Wallowas, layers of rock - flat, folded or stacked side-by-side - provide a visual tour through our planet's history.

Here along the canyon of the Powder River, the uppermost and youngest of these rocky layers are particularly prominent. These are the Columbia River Basalts, formed by massive lava flows that repeatedly inundated this region over millions of years.

For several days, heavy rains had soaked the dry foothills above the Powder River. The water had percolated through the soil to the basalt bedrock below, then continued downward through cracks in the rock, where it seeped into an underlying layer of clay below the basalt. The tilted basalt layer had resisted the pull of gravity for millennia. But heavy rains - and possibly some small earth tremors - finally set the system in motion. Like a pile of bricks on ball-bearings, the basalt blocks slid across the wet clay and tumbled downhill.

The slide continued to creep downhill, at up to a half-inch a day.   The debris choked the Powder River, creating a half-mile-long lake.

When this event first took place locals noticed springs drying up and rocks popping off the hill side like popcorn. Soon the earth started shifting and gradually filled in the draw causing the road to be closed and the river to take on a new form. The current bypass is located where a temporary road was first installed.

When this event first took place locals noticed springs drying up and rocks popping off the hill side like popcorn. Soon the earth started shifting and gradually filled in the draw causing the road to be closed and the river to take on a new form. The current bypass is located where a temporary road was first installed.  

Logging Requirements

First:  To get credit for this cache please email the cache owner the answer to the following questions:

1.  What is the amount of dirt this slide moved? (estimate)
2. This amount of earth is equivalent to a line of dump trucks reaching from Baker City to where and back again?