Looking roughly south to southeast from the deck at the top of the stair to the beach, we're overlooking the wave-cut platform and tidepools at Cobble Beach on the south side of Yaquina Head. Newport, Oregon is on the shore in the far left. Though you'll have to enlarge to see most of them, there are numerous people in this panorama who provide a sense of scale.
Another example of radial jointing with Dana for scale. As with the previous example, I suspect this was something like a cylindrical conduit or tube in which the basalt initially flowed, then stopped and cooled in place.
Returning to Yaquina Head after a three day diversion to the top of Marys Peak, this is one of several fairly recent (quite fresh and unweathered) boreholes in the cliff face along the south shore. I suspect this was a core taken for paleomagnetism studies. Certain kinds of rock can fairly effectively record the inclination and bearing of the earth's magnetic field at the time they were formed. If the rocks are displaced north-south, or rotationally (unfortunately, east-west movement isn't detectable with this method), differences between the recorded magnetic field and the modern one can be discerned.
A view similar to Monday's panorama, but a single shot. Mount Jefferson is visible in the gap in the trees to the left, and Three Sisters, somewhat obscured in low clouds, can be seen near the center. I suspect there are viewpoints less obscured by trees farther up the summit trail, but we were time constrained on Saturday, and I no longer have the stamina to tackle even a portion of that trail lightly. Unless the viewing is excellent, I'm not going to wear myself out trying.
Looking east out over the Willamette Valley from the top of Marys Peak, the fault marking the boundary between the valley floor (forearc basin) and the Coast Range (forearc ridge) is pretty obvious. The fault itself actually sits about 1 1/2 km (1 mile) in front (east) of the prominent ridge. This sort of landform, where the escarpment runs parallel to the fault, but not on the fault- typically because erosion has beveled the ridge back- is called a fault line scarp. This differentiates it from a fault scarp, which is taken to mean that the ridge accurately marks the location of movement.
The Corvallis Fault is stitched by gabbroic/diabasic intrusions of Oligocene age, contemporaneous with and similar to the Marys Peak Sill. These intrusions have not been broken tectonically, providing good evidence that our neighborhood fault has not been active for roughly 30 million years. Despite its proximity to town, it's not one we need to worry about with respect to seismic hazards.
1st photo unmodified; in 2nd, contrast ramped up and annotated in Paint.net. June 22, 2013. FlashEarth location.
The view on Saturday looking out over the Willamette Valley (forearc basin) to the Cascade volcanic arc. Mount Jefferson on the left (north), Three Sisters on the right (south). We're standing on Marys Peak, the highest point in the Oregon Coast Range, the forearc ridge. It's difficult to describe how profound this view is to me; we're looking at a fundamental component of the earth's engine.
Yaquina Head, and another of the coastal occurrences of Columbia River Basalt, Cape Lookout, give the appearance of channelized flows- that is, the basalt flows in these two locations don't appear to have spread out on a wide coastal flat, but seem to have been confined to a relatively narrow channel. As a result, both consist of a resistant "finger" of rock sticking out into the ocean. I don't know whether Cape Lookout has a lighthouse, but many of these rocky headlands, including Yaquina Head, do.
In addition to creating navigational hazards to marine travelers, fingers like these two are obstacles to whales that migrate from south to north then back again each year. They tend to travel where the water is a particular depth, and will swim up to protrusions like this, then turn out to sea to get around them. As a result, spots like this are among the closest they get to land- to the delight of sightseers. On this day, there was a good crowd on the west side of the lighthouse whale watching. I personally didn't see any spouts (nor did I spend much time looking; too eager to go look at rocks), but they assured me there were two or three whales passing through at the time.