Royal Gorge

Points of Interest:

• See ancient rhyolite rocks from your windshield.
• See gnarled blackjack oaks clinging tenaciously to life on the rocks.
• Explore the boulder filled Big Creek.

Natural Features Description:

A billion years ago this landscape was dominated by active volcanoes. Much like the Hawaiian Islands today, these volcanoes rose above a surrounding sea. Magma flows over the surface cooled to form rhyolite the rock seen here. This rhyolite has been aged at 1.5 billion years old! Over millennia the volcanic mountains here have slowly weathered to the knobs we see today like that here at Royal Gorge. This gorge is referred to as a shut-ins. Shut-ins occur where a broader stream is “shut in” to a narrow canyon-like valley. In Missouri, shut-ins typically are found where streams flow through softer sedimentary bedrock such as dolomite and then encounter more resistant rock like rhyolite. Rhyolite is considered an igneous rock, one formed from magma, molten rock.

Above the creek valley the vegetation is stunted growing on the open rhyolite rocks with a western exposure. These igneous glades provide harsh growing conditions. Short-statured and gnarled blackjack oaks are scattered across the rock outcrops.

Along the creek valley the rare winterberry and northern arrow-wood occur. Both of these species are only found in the Ozarks in Missouri and only at scattered locations along rocky streams such as this. They provide fruits valuable to songbirds.

In the creek lives the Big Creek crayfish. The world-wide distribution of this crayfish species is restricted to the St. Francis River basin of Iron, Madison and Wayne Counties. This crayfish prefers small, high-gradient rocky creeks. Unfortunately the introduction of crayfish species not native to the St. Francis River basin can cause problems for the Big Creek crayfish. Inter-basin transfers of crayfish species through bait bucket dumping and other methods have caused declines in many endemic crayfish populations.