Rock seems quite solid, doesn't it? Many features, however, such as joints, faults and random fractures act as conduits for root growth, slow percolation of water and weathering far below the earth's surface. Such weathering not only produces soil for plants but some fantastic shapes, such as spheroidal "onion skin" or tombstone boulders.

No, we aren't talking about funny cigarettes or seedy bars. Geologic joints are the most common of brittle fracture systems in rocks. They're produced by a variety of causes: shrinkage due to loss of water, cooling of magma, relaxation features resulting from the removal of stress (we could all use a little of that!) or tectonic stress (pushing or pulling on brittle rocks).

Principles of relative-age dating allow geologists to understand which rocks are older than others, but they don't reveal how old they are in years.

No, the term "relative age dating" does not refer to a socially taboo subject, just a series of logical observations, called principles. They were developed long ago to assess which rock units are older, in a relative sense, than others.

Have you ever seen imaginary objects in cloud shapes? That's what's so creative about our human minds: We can look at them and imagine we see animals, a pirate ship or Elvis.

Change is the only constant, and that's true of the Rogue Valley's climate, which hasn't always been the same.

Fossils are of interest to most everyone, even to those of us slowly becoming fossils.

The magnificent High Cascade volcanoes are relative youngsters, built on the surface of older, slightly tilted and deeply eroded Western Cascade volcanoes. In our area, the oldest High Cascade lavas are represented by the 7-million-year-old Table Rocks.

All of us are enthralled by the large, High Cascade volcanoes such as Mount McLoughlin and Mount Shasta. But did you know there were much older but just as impressive volcanoes, now humbled by erosion, forming the northeastern ridges of our valley?

Keeping one eye on the road, another on an unruly child and a third on the yellow-brown cliffs on the northeast side of the Rogue Valley, one might wonder how those cliffs originated.