Geology Is Messy: Lime, Oregon

Informal monument to the late Lime, Oregon

You won’t find Lime, Oregon on a map; at least not one published in the last forty years. Lime isn’t even a ghost town; it’s obliterated, along with the cement plant that was Lime’s reason for existence. Today, Lime is a wide spot in a side road off Interstate 84, not too far from Baker City.

Approximate location of the terrains comprising the Blue Mountains. Lime is located between Baker and the Snake River as it enters the block diagram

Lime is lost because of geology. The limestone outcrops that fed the cement kilns at the vanished cement plant were a part of the Triassic Martin Bridge Limestone. You see, part of the rocks that make up the Wallowa Mountains today originated as a volcanic tropical archipelago of islands in the southwestern Pacific Ocean. The islands were surrounded by reefs, as tropical islands frequently are. The reefs and the marine life built up impressive depths of limestone as the islands slowly moved across the Pacific, before colliding with the North American craton about 150 million years ago. The limestone was a comparatively small portion of the Wallowa Terrane, which also included older volcanic rocks and sedimentary rocks.

The collision of the small tectonic plate bearing the tropical islands and the North American plate was, as these things are, messy. Some of the limestone got scraped off; other parts got buried. Much later, the Columbia River Basalts happened, burying much of the native rock under hundreds, sometimes thousands of feet of basalt.

The volume of basalts erupted in that extreme volcanic event altered the isostatic balance of the area. By a process that is still being sorted out by geologists, the Wallowa Mountains rose up more than twelve thousand feet, to become the mountain range they are today. When they rose, they carried chunks of that shattered limestone apron up with them. Sacajawea Peak, the highest peak oil the Wallows, is composed mostly of limestone.

Abandoned limestone quarry, Lime, Oregon. Imnaha basalts behind and above; benches from mining visible below

One of those chunks of shattered limestone was located along what’s now the U.S. 30/Interstate 84 corridor. It was the source material for the plaster and cement plant built at Lime in 1916. The plant operated until 1980, when nearby limestone formations were exhausted. If it’s made of concrete and in eastern Oregon or southwest Idaho, it’s probably cement from Lime.

(Portland cement is made by heating limestone, calcium carbonate, with other materials like clay to 1,450 °C (2,640 °F) in a kiln. The process is called calcination. The extreme heat causes the limestone molecules to lose a molecule of carbon dioxide, to form calcium oxide, or quicklime. The quicklime reacts with the clays and other additives in the mix to form calcium silicates and a suite of related compounds. The product is a spiky, lumpy rock called “clinker,” which is then ground with a small amount of gypsum (CaSO₄·2H₂O) into a powder to make ordinary Portland cement, the most commonly used type of cement.)

Cement isn’t the only industrial use of quicklime. But it’s overwhelmingly the most important. Cement prices drive the industry.

Spilled clinker mound, Lime, Oregon

A railroad spur provided low cost transport of the finished cement. The railroad siding, some scraps of metal and cable and piles of limestone and clinker are pretty much all that is left.

Today, there’s another, slightly newer cement plant five miles away from Lime, mining another set of Martin Bridge Limestone outcrops. The intermittent nature of the deposits, the cost of hauling raw limestone ore any distance and the comparatively low margins in lime manufacture mean that before too long, that “new” plant will exhaust nearby limestone deposits and a newer plant will be built near another outcrop.

The geology, the discontinuous, scattered remnants of the Triassic limestones, meant the beginning and end of Lime. Geology is messy.