Tom Schweich  

The reason to take US Hwy 91 south rather than I-15 would be to view the spillway of Pleistocene Lake Bonneville into the Snake River drainage at Zenda and Red Rock Pass.

Zenda

Zenda is given as the location of an alluvial dam that held the highest stand of Pleistocene Lake Bonneville for 500 to 1000 years before it eroded, creating the Bonneville Flood.

Red Rock Pass

Hill with monument	Interpretive Panel for Red Rock Pass	Interpretive Panel for Red Rock Pass	Memorial plaque to Captain Jefferson Hunt	View from top of hill

Red Rock Pass Geological Site About 14,500 years ago, ancient Lake Bonneville overflowed at this site. A dam of alluvial fans between Oxford Mountain to the west and the Portneuf Range to the east suddenly eroded releasing Lake Bonneville from the Great Basin into the Snake River system. The Peak flow was about one million cubic meters per second at the pass, or about 500 times the maximum discharge on the Snake River at Idaho Falls, Idaho. Ancient “bathtub ring” shorelines up to 1,000 feet above the valley floor are readily visible in the Salt Lake Valley. Evidence of the flood is visible thoughout southern Idaho with areas of scoured bare bedrock (“scabland”) and deposits of boulders (“melon gravel”) marking the flood path. After about 11,000 years, Lake Bonneville receded to become the Great Salt Lake. Highly saline and only 40 feet deep, it is but a shadow of giant fresh-water Lake Bonneville. Red Rock Pass is the geographic northern extremity of the Bonneville drainage basin, and was also designated by the early Latter-day Saint leaders as the northern edge of the proposed State of Deseret. North of here, water flows to the Snake, Salmon, and Columbia rivers, on the way to the Pacific Ocean, but south of here it flows into the Great Basin and the Great Salt Lake. South of the monument in Red Rock Pass, the house-sized limestone blocks were jostled during the breakout of the Bonneville flood. The uneven topography northwest of the monument is a landslide which flowed into Red Rock Pass after it was deepened about 400 feet during the flood. Ancient cave formations are found in the flat-lying limestone of Red Rock Butte immediately north of the monument.

Red Rock Pass You are standing in the outlet of ancient Lake Bonneville. A vast prehistoric inland sea, of which Salt Lake is a modern remnant. Covering over 20,000 square miles when it overflowed here about 14,500 years ago, its winding shoreline would have stretched from here to New Orleans if it were straightened out. This pass was deepened considerably when Lake Bonneville began to slow into Snake River. For a time, a torrent several times larger than the Amazon was discharged here. Finally, with a hotter, drier climate that slowly emerged about 8,000 years ago, Lake Bonneville gradually disappeared.

No 119 Erected October 2, 1950 Captain Jefferson Hunt, Soldier, Pioneer, Churchman Charles Jefferson Hunt served in the Mormon Battalion as captain of Company “A” and as assistant executive officer, in its historic march from Council Bluffs, Iowa to San Diego, California, 1846-47. His service won the commendation of all who served with him. Under appointment by President Brigham Young in 1851, Captain Hunt was guide for the pioneers to San Bernardino, California. His pioneering service included also Provo, Parowan, and Huntsville (which bears hus name), in Utah, and Oxford, Idaho. A convert to the church of Jesus Christ of Latter-Day Saints he was loyal, obedient, and faithful to the end. Erected by descendents of Captain Hunt and the Utah Pioneer Trails and Landmarks Association.

To the south, US Highways 89 and 91 share a route over Sardine Summit,

Logan

Logan

Junction: US Highway 89, south to Salt Lake City, Utah, or north to Logan where the routes diverge.

Brigham City

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