REVISITING A POPULARIZED GEOMORPHOCOLOGICAL INTERPRETATION: UPPER AND LOWER TABLE ROCK, MEDFORD, OREGON
The notion that the buttes are representations of inverse topography comes from a number of observations. The horse-shoe shape of each butte suggests to the mind the arcuate shapes of river meanders. The buttes’ proximity to the present-day Rogue River tempts one to think that the ancestral Rogue River could have anciently carved a meandering channel for the lava to follow. Being more resistant than underlying mudstones and sandstones the capping lava would have naturally protected the underlying sediments from erosion and forced the river to move elsewhere. With the passage of time, some of the ancient meanders would have been preserved while the river graded the rest of the valley.
The latest Google Earth satellite imagery restores an alternative interpretation, which is not new at all, but which was explicitly advanced by Smith and others in 1982: the lava flow or flows were valley-filling rather than channel-filling. This view is supported by the vast scale of the mapped distribution and thickness of andesite of Table Rock outcrops. New terrain data derived from Google Earth cross-sectional profiles show that the thickening and thinning of outcrops at the Table Rocks are at odds with the downstream direction of flow of a fluid lava following and confined to a pre-existent channel. Though a scientific notion may be advanced by popular publication, that view may not necessarily be supported by the full weight of the scientific evidence.