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Thousand Springs

Park manager David Landrum stands near Hidden Lake near Thousand Springs in 2012 near Hagerman.

Why is the scenic Hagerman Valley considered the banana belt of southern Idaho?

A banana belt is defined as any segment of a larger geographic region that enjoys warmer weather conditions than the region as a whole, especially in the wintertime.

“I believe that Hagerman is called the banana belt because the temperature is usually a few degrees warmer than the surrounding towns,” said geologist Art Small. “I have heard Riggins called the banana belt also. The warmer temperatures are because of the low elevation and the canyon with black rocks, which absorb heat from the sun and radiate the heat down into the canyon.”

Banana belts refer to areas with a warmer, milder climate, said Shawn Willsey, professor of geology at the College of Southern Idaho. “Hagerman is about 800 feet lower in elevation than Twin Falls and in a wide valley. Additionally, the numerous springs in the area provide water for a large riparian ecosystem. As the area lies below the canyon rim, it is somewhat sheltered by winds at times.”

The Treasure Valley area around Nampa is known as Idaho’s Banana Belt.

With Lewiston located at the confluence of the Snake and Clearwater Rivers, it is known as the “Banana Belt of the Pacific Northwest.” Residents enjoy year-round golfing, while being only a short drive away from snow skiing. The elevation is 738 feet above sea level.

Kari Prassack, paleontologist for Hagerman Fossil Bed,s said Hagerman Valley is called a “banana belt” because it is an area that receives warmer weather and less snowfall than the areas surrounding it — like a belt of the “tropics” in Idaho. “This happens because warm air lifts upwards over the mountains, expands and cools, producing rain. And then, as drier air, it descends along the other side — in this case into the valley here where the air compresses and warms.”

Prassack was asked if dinosaurs gravitated to the Hagerman Valley because it was warmer. She said Idaho has some fossils that date to the Mesozoic (age of dinosaurs) but Hagerman’s fossils are much more recent — only 3 to 4 million years compared to over 65 million. “The climate of all of North America was much warmer and wetter during the Mesozoic than it is today. As a result, there were dinosaurs living as far north as Alberta, Canada and even up above the Arctic Circle. The Hagerman Valley did not even exist back then. It was formed by the Bonneville Flood a mere 15,000 years ago,” said Prassack.

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