Geological history

More than 10.8 million years ago, sediment began to accumulate in the area, as shown by the age of overlying volcanic ash deposits found near Arock, located a few miles east of Rome. The sediment was deposited in a large basin that formed here after the Yellowstone Hotspot passed nearby and basin and range faulting began; it’s just one of the several basins that define the Lower Owyhee River corridor.

About 2 to 5 million years ago, after the sediments were deposited, the ancestral Owyhee River, together with its tributary Crooked Creek, started to carve out the Rome valley. Weathering and the erosional activity of these watercourses shaped the landscape, gradually forming the valley as it appears today, including the scenic badland formations that pioneers called the “Pillars of Rome.”

The best way to experience the badlands and striking rock cliffs is to take a drive along Kiger Road, north of Rome Station on US-95. (See map.) If time allows, take a short hike through the sagebrush to any cliff and try to guess which, if any, layers of sediment were deposited in lake water (lacustrine), and which were deposited by a stream or flood (fluvial).

Before the Owyhee River existed, a series of poorly connected shallow lake basins (including this one) probably occupied today’s river corridor from Rome to the Oregon-Idaho border. Downstream (north), the river corridor is lined with sedimentary strata like we see here in the Rome valley. The sediment changes somewhat when the river crosses into a new basin, each of which has its own history of local volcanic eruptions and sources of sediment, and possibly a different history of faulting and uplift. But in general, the Rome valley story applies to the sediment found throughout the Owyhee River corridor all the way to Lake Owyhee.

The Rome valley sediment beds

At least three research papers have been published on the Rome sediment beds. The research shows that sometime between roughly 12 and 15 million years ago—before the first sediment—two thick lava flows flooded the basin floor. First came a basaltic lava flow, then a rhyolitic lava flow. Both lava formations are now visible at the northern end of the valley, where the strata have experienced modest uplift relative to the central valley. Researchers think these lavas underlie the entire Rome valley—its bedrock.

Streams and intermittent floods then carried material from surrounding volcanic highlands and deposited it onto gently sloping mudflats and floodplains in the basin, creating layer upon layer of coarse-grained sediment. At times a shallow lake formed that saw many changes in water level (including drying up) which caused the shoreline to frequently advance and retreat. Intermittent eruptions from nearby volcanic fields sometimes covered the basin floor with lava flows and volcanic tuff (ash and rock fragments), some of which were deposited in standing water. Over time, it all cemented into the multicolored rock layers that we now see in the valley walls. Eventually sediment filled up the basin, and it was probably roofed over by one or more lava flows—like the gently sloping lava plateaus we drive through on the way to the valley today. All this happened long before the Owyhee River existed.

In the final basin-filling phase, a long-lasting perennial (year-round) freshwater lake formed near today’s Crooked Creek State Park. It’s unclear whether it covered the entire basin or just a small area. The lake left behind an approximately 100-foot-thick layer of very fine-grained lakebed sediment containing abundant fish skeletons and vertebrate bones, including beaver. This fine-grained sediment is exposed below the Crooked Creek canyon rimrock, near US-95. The fish skeletons and vertebrate bones are from animals that we know lived between 4.8 and 9.0 million years ago, giving us a date range for the age of the lake.

Sediments exposed by US-95 roadcut

A good place to see freshly exposed layers of the Rome valley sediments is in the roadcut along US-95 where the highway descends into the valley. Here the sediment has been preserved beneath a protective lava rimrock. Elsewhere in the valley, the topmost sediments are often buried under lava flows or eroded away. The thick, light-colored layer in the roadcut is a bed of volcanic ash likely older than 1.5 million years based on overlying dated lava flows.

New lakebed sediment deposited

Geologists discovered a layer of fine lakebed sediment at about 3,600 feet elevation in the Rome badlands, indicating that as the Owyhee River carved out the valley, lakes formed and deposited fresh sediment over older layers.

The lakes developed when lava flows from periodic volcanic eruptions on the surrounding plateau created temporary dams that blocked the Owyhee River. The lakes behind the lava dams sometimes extended many miles upstream and submerged the Rome badlands. Fine, light-colored sediment in the lakes settled and formed new layers over the older, coarse-grained Rome badlands.

Published and ongoing research suggests that because of multiple large lava blockages that occurred downstream from about 1.9 million years ago to 600 thousand years ago, the Rome valley has cycled between a lake and a through-flowing river multiple times.

Zone of hydrothermal alteration above Rome boat launch

A fantastic exposure of hydrothermally altered basalt and sediment lies just a short hike uphill from the gravel access road to the Rome boat launch. An excellent place to see what happens when a lava flow encounters water. The Owyhee canyon is well known for its many examples of lava-water interaction, several of which are pictured and described in later chapters.

The lava flow erupted from a vent on Round Mountain about 1.7 million years ago and spilled into the Rome valley, which was possibly then filled by one of the short-lived lakes described earlier.

The heat of the incoming lava was so intense that it baked (fired) the underlying water-saturated sediment into a hard, clay-like rock. A short-lived but intense hydrothermal condition existed. Temperatures reached hundreds of degrees centigrade, water flashed into steam, the steam and super-heated water migrated through the wet sediment and into the overlying lava. Sediment was injected upward into the lava and soft lava sagged downward into the sediment, forming the “peperite” structures visible in the sediment-lava contact zone.

As the steam and super-heated water migrated upward into the overlying lava, it fractured the base of the lava into blocks that allowed hot water to circulate through it for a short time. Once fractured and permeable, the hot water and steam chemically altered the lava at the base of the flow into a zone of clay minerals and palagonite material.

At this site, peperite and altered lava help confirm that the flow entered a wet valley floor, supporting the interpretation of a lava-dammed river environment.

Evidence of ancient riverbed

Researchers have discovered signs of an ancient riverbed about 1 to 2 miles west of the current Owyhee River, possibly dating to over 1.9 million years ago. If confirmed, this means that by about 1.9 million years ago, about 140 feet of today’s 340-foot-deep valley was already exposed. That’s over one-third of the valley’s present depth. The river later shifted eastward, further widening the valley.

Evidence for the ancient riverbed consists of an unusual layer of river-rounded rocks and gravel about 200 to 230 feet above today’s river level. These rocks lie beneath the layer of distinctive white lakebed sediment thought to have been deposited 0.6 to 1.9 million years ago when several lava dams blocked the river downstream. (Described earlier.)

Ice age outburst flood enters Rome valley

It’s hard to imagine that the largest floodwaters yet documented in the Owyhee River canyon came down Crooked Creek. Today it’s a small brush-filled tributary stream—not given a second glance. (See photo.)

The flood(s) occurred 13,000 to 18,000 years ago, at the end of the last glacial advance. The floodwaters came from Alvord Lake, one of the many large lakes that existed at the end of the ice age in the high-desert region of the west. At its peak size, it was about 70 miles long and about 270 feet deep. Today it has little water and parts of it are known as the Alvord Desert. (See photo.)

At its largest, the lake overflowed into the Owyhee River via the Crooked Creek drainage. Abundant flood evidence exists. Along Crooked Creek geologists have found eroded canyons, scoured bedrock surfaces, scabland topography, numerous boulder bars and 15-foot boulders left stranded more than 100 feet above the present channel.

Based on the size of the lake and the topography and constrictions of Crooked Creek, geologists determined the peak downstream flood was about 350,000 cfs (cubic feet per second); 6x larger than the highest water flow (55,000 cfs on March 18, 1993) recorded on the Owyhee River since records began in 1950. The flood lasted at least 13 days, probably much longer.

As the floodwaters entered the Rome basin, they fanned out and flooded the valley upstream to the US-95 highway bridge. The shallow lake in the Rome valley lasted several weeks.

Though the evidence is much less complete, it’s plausible that another older and much larger outburst flood occurred. Geologists identified an older (and higher) Alvord Lake shoreline that indicates older periods of overflow into Crooked Creek and the Owyhee River. They also found flood deposits and drainage topography along Crooked Creek that could only have been created by a large flood with a peak discharge of 1.4 million cfs. The postulated older flood is 4x larger than the flood that occurred 13 to18 thousand years ago, and 25x larger than the highest modern water flow recorded on the Owyhee River since records have been kept.

History note: Owyhee Crossing

Rome Valley lies along a key route linking Idaho with Oregon and Nevada. It’s one of the rare spots in SE Oregon where travelers can cross the steep, narrow Owyhee canyon without difficulty. Archaeologists believe that people have used the river crossings here for thousands of years.

Gold miners and pioneers gave the name “Owyhee Crossing” to the well-used river ford. Before the steel bridge was built in 1906, travelers either waded across the river during low water or paid a toll to ride a seasonal ferry during high water.

1860s wagon road: For about 20 years starting in 1863, this was an important and heavily used road that carried freight from California to the newly discovered gold mines in the Owyhee Mountains southeast of Jordan Valley. Initially it was a system of trails traveled on horseback with packtrains. By 1866 a toll road (the “Skinner Road”) had been built from the ford at Owyhee Crossing through the Jordan Valley and up to the mines, finally allowing wagons and stagecoaches to travel the route. Stagecoaches took days, freight wagons took weeks to reach Ruby City and Silver City (now ghost towns) from the nearest railroad at Winnemucca, Nevada. The road remained a heavily used wagon supply route until railroads finally reached Idaho in 1883. The old wagon road still exists and can be traced on Google Earth through the sagebrush from Owyhee Crossing to the Oregon-Nevada border.

Settlement in this rugged, arid corner of Oregon was minimal until gold was discovered in the Owyhee Mountains in 1863, leading to a rush of miners and the creation of several ranches along Jordan Creek for food supply. A part-time ferry was soon set up at the Owyhee Crossing in 1864 to help cross the river during high water. Rome valley’s first permanent structure was likely a simple two-person stone house occupied seasonally by the ferry operator and assistant.

Native Americans: The Owyhee region was home to the Northern Paiute people. As miners moved into the area, a series of armed conflicts—often referred to as the “Indian Wars”—made the Owyhee Canyon and Rome Valley unsafe for non-Native settlement until sometime after about 1878.

Homesteads: Clint Duncan received the first homestead patent in Rome Valley in 1900, having purchased the ferry operation at Owyhee Crossing and settled there in 1892 according to oral accounts. He continued running the ferry until the steel bridge was built, using a hand-crank/winch mounted on the ferry deck to pull the ferry across the river. In 1909, Duncan received approval to establish a post office named “Rome” inside his home. He continued running the ferry until the steel bridge was built. In 1911, his son constructed a stone house just downstream from the bridge, five years after the ferry stopped running.

By 1915, more settlers had moved into Rome Valley, leading to at least five officially patented homesteads along the river. At one time there were six water wheels in operation along the river to lift irrigation water into ditches supplying fields. (See Chapter 13, Birch Creek Ranch, for discussion of water wheels.)

Community of Rome: The small, unincorporated community of Rome is named after the post office set up by Duncan in his home in 1909. The post office moved between several ranches until it was closed in December 1933, after which the nearby community of Arock handled mail services.

The US 95 highway bridge over the Owyhee River was built in 1936 to support growing automobile traffic and the new U.S. highway system, replacing the smaller single-lane steel bridge and dirt road located three miles downstream. By the mid-1940s, Rome Station, comprising both a café and an automobile service station, was in operation near the new bridge.

Sources

(Sheppard & Gude, 1987), (Campion, 1979), (Ellison, 1968), (Wolf & Ellison, 1971), (Walker, et al., 1974), (Fretwell-Johnson, 1990), (Skinner, 2025), (Carter, et al., 2005), (Personius, et al., 2007)