The bedrock threshold over which the Lake Bonneville emptied is covered by post-Bonneville alluvium and colluvium. A 12-channel seismograph was used to determine the exact position, configuration, and altitude of the original pass. The elevation of the crest probably exceeds 4,755 feet by one or two feet over most of the length. The width of the channel on the crest is about 800 feet. The threshold trends N. 85 degrees W., oblique to the channel, which trends N. 30 degrees W. The slopes approaching the threshold are steeper on the east side of the channel, perhaps indicating that the threshold is slightly lower on the east end, and that in the last stages of flow, the stream was at the east side of the channel. The depth of the fill on the threshold is about 20 feet.