When the flow of thick lava cools off on the earth’s surface, it forms fractures. If the flow is horizontal and cools quickly, it cracks and forms columns. Thus forming columnar basalt, which you see across the river.
Once the crack develops it continues to grow perpendicular to the surface of the flow. The size of the columns depends on the pace of the cooling.
The columns form sets. The straight columns are called ‘colonnade’. When the cooling is caused by fresh lava being covered by water, the columns curve. These curved columns are called ‘entablature’.
In most cases there are five or six sides to these columns. But anywhere from three to twelve sides have been observed.
Columnar basalt can be observed in many parts of the world. There are several examples in Oregon including those at Crater Lake and Toketee Falls. You will also find them, if you travel to Washington and/or Idaho. These are all 12 to 17 million years old.
Excellent videos can be seen on YouTube about the Columbia River Basalt Group, which formed in the Ice Age Floods from Glacial Lake Missoula. It covered 59,000 square miles here in the Northwest.
We’re not rating this wheelchair accessible, but the columnar basalt can be seen from a vehicle.
Please log you visited this area, then e-mail your answers to the following questions:
- Is this colonnade or entablature?
- On average, how many sides does each column have?
- Using your imagination, of what does this remind you?
- Optional: What do suppose the green on the surface is?