The Basaltic cliffs of interest are to the east. Pull over fully before attempting to read the description and logging requirements.
What you are looking at is geologically the same as the most famous of these Basalt columns, the Giant's Causeway in Ireland Link
Logging Requirements:
- Estimate where on the hill the basaltic columns are located (bottom, mid, upper, top)
- What percentage of the cliffs display the basaltic cliff spire formation?
- Based on your reading AND observation, do you believe the cooling was slower or more rapid?
So why do these basaltic cliff spires form?
During the cooling of a thick extrusive (above ground) lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form (that is why THICK LAVA is a necessary prerequisite). The extensive fracture network that develops results in the formation of columns. Because hexagons fit together efficiently with no vacant space, this is the most common pattern that develops. Pentagonal, heptagonal or octagonal joint patterns are also known, but are less common. Note that the size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small columns while larger columns often form in environments cool more slowly.
Resources:
http://www.nr.gov.nl.ca/mines&en/geosurvey/publications/cr1999/dickson.pdf
wikipedia "basalt columns"