These roadcuts provide a window onto bedrock that would otherwise be rarely if ever seen. They reveal geology that has been broken up over a huge area at some point in the past, and laced with intruding quartzite, producing the kinds of marbled patterns seen in the above photograph, taken along I-495 in northern Massachusetts. Some veins are very wide, while others are narrow, but they are usually fairly uniform in width. Roadcuts show that the bedrock over huge portions of Massachusetts and New Hampshire exhibits this marbling.
The pattern is reminiscent of the marbling found in the Black Canyon of the Gunnison, in Colorado, which Walt Brown discusses in his book discussing the evidence supporting the hydroplate theory, which can be found online in its entirety. Dr. Brown provides massive amounts of evidence from a wide variety of physical sciences which support his theory -- evidence ranging from ocean trenches, to Arctic and Antarctic fossils, to subglacial Antarctic lakes, to coral atolls in the Pacific, to submarine canyons carved into the continental shelves below the current levels of the oceans, to the geographic strata found around the world, to specific aspects of the Grand Canyon, to petrified wood, to the sediments along the southern edge of the Himalayas, to clues found on the moon, on Mars, on asteroids, and in the behavior of comets (and many more areas besides those).
In his examination of the Black Canyon of the Gunnison, Dr. Brown explains that the geological evidence points to violent forces in the past which were able to fracture the darker rock over an enormous area, in conjunction with forces capable of injecting liquid quartz throughout the fractured rock before hardening. He observes that a fairly unique set of conditions would be required to produce such a "marble-cake" appearance, because in most circumstances the quartz would harden before it went very far, and would tend to only travel through the widest path of least resistance (or at most on only a small number of most conducive channels) rather than lacing the entire rock over vast geological distances.
He argues that the conditions that would leave such a "marble-cake" appearance are consistent with the violent forces that would have been present during the events proposed by his hydroplate theory. A full explanation of his reasoning can be found in his own words here (scroll down to the inset about the Black Canyon of the Gunnison, entitled "A Picture with a Story").
In sum, he demonstrates that the forces typical of those proposed by the dominant tectonic theory (stretching forces or compressing forces acting in one direction over a long period of time) would not explain the extensive fracturing found in the Black Canyon. Only the kind of rapid crushing that would have taken place over huge areas during the compression event described by his hydroplate theory (when the plates slid after the initiation of the flood, and then came to a violent stop accompanied by massive compressive forces similar to a car crash or a train wreck) could have produced the widespread fracturing found in Colorado.
The fact that the same types of forces appear to have acted on huge swaths of New England as well argues that these crushing forces were very widespread. He points out that it seems far more likely that one worldwide event led to this widespread rock crushing, rather than that the very complex conditions required to produce such crushing just happened to "crop up" over and over in various parts of the world.
He then points out the difficulties involved in lacing this crushed rock with the bands that we see today:
The hydroplate theory explains how deep magma was produced in large pockets under the bedrock during the period of rapid drift, when the plates were sliding away from the area that became the Atlantic Ocean towards the great hole that was forming to make the Pacific Basin. The immense friction during this sliding event melted rock into magma.
Next, magma must rapidly squirt up through the cracks in the black rock. If it happened slowly, or even at the rate a river flows, the front edge of the upward-flowing magma would solidify (freeze), stopping the flow. If water is dissolved in any molten rock, its melting temperature is lowered considerably. Therefore, melted quartz with dissolved water would be more likely to complete the cold, upward journey.
Each channel (or vein) at the Black Canyon has a fairly uniform thickness. This reveals that the liquid’s pressure exceeded the rock’s pressure by nearly the same amount all along the channel. Again, this would not happen if the flow were slow or had the consistency of cold tar.
This marble-cake appearance is exposed for at least 50 miles along the Gunnison River, so the compressive force must have been about the same over at least those 50 miles. Magma, if it came from one spot below, would tend to escape through the shortest cracks leading to the surface. Instead, magma has filled cracks over a 50 mile range. Consequently, the magma source and any water were probably spread over a large area directly below.
The presence of such marbled rock over very wide areas in New England, in addition to the massive formations that Dr. Brown discusses in Colorado at the Black Canyon of the Gunnison, appears to provide another piece of geologic evidence that supports the hydroplate theory and which is better explained by that theory than by existing tectonic theories that build their explanations on the work of long, slow, non-catastrophic forces.
The next time you have the opportunity to drive through northern Massachusetts and southern New Hampshire, be on the lookout for roadcuts that provide a fascinating look into the bedrock, and the tale of violent crushing and marbling that remains etched into the stone for us to observe to this day.