HARRIS BEACH UNDERWATER STRUCTURE

researched by: Russell Ralls (retired geologist)

Type: Simple (proposed)
Diameter: ~137 metres
Depth: ~15 metres
Location: Brookings, Oregon (off-shore), USA 42.062312° N 124.31438752°W
Age: >10,000 years^a

^a More than 10,000 years ago during last Glacial sea level along Oregon was about 50 to 60 meters lower than it is today. If the “Feature”, Crater or hole had formed during last Glacial it would have been dry land and subject to advancement of sea level rise and would have been filled in with sand, silt and gravel during the very active environment of surf and beach conditions. (Ralls)

Structure bedrock is Dothan Formation of late Jurassic consisting of hard chert on the western half and hard sandstone/siltstone on the eastern half. Possible but unconfirmed part of eastern bedrock could be Oligocene Rhyolite dike intrusive, as outcrop of Rhyolite is within 200 feet of the eastern minimal 450 foot diameter rim. Immediately adjacent to the hole on the west side is a Dothan age outcrop of massive Chert, so that the western slope of the hole are chert. The northern, eastern and south slopes in and around the rim are composed of rocks and sand debris. Slopes around the hole are about 25 to 35 degrees plunging down in a conical feature. Navionics bathymetry. (Ralls)

My diving today starting at the rhyolite dike about 600 feet east of the rim of the site and swam on bottom SSW towards the hole. The Ocean bottom in the first 400 feet after leaving the rhyolite intrusive consisted of big car to house sized boulders and blocks composed of rhyolite [an igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface] sloping down to about 64 feet deep. At 64 feet deep the bottom leveled out changing to smaller boulders, rocks and cobbles. Continued swimming SSW the bottom began to slowly rise until the upper edge of the rim at about 50 feet deep. I swam on bottom along the upper edge of this rim northward to the north end of the rim staying at the 50 foot level. At the north end of the rim I continued swimming on bottom north towards shore and noticed the bottom depth increased back to 60 foot depth before again rising towards shore 1/4 mile away.

Today’s dive showed without question that the hole has a raised rim around its eastern and northern sides just as the bathymetry chart map shows.

Underwater Crater Explorer, Russell J. Ralls, Professional Geologist.

Magnetic sample from the structure. The black sands have low density and are soft, therefore they are not magnetite, Illemenite, chromite or any of the spinel group minerals that are magnetic or para-magnetic. Also I don’t think they are minerals as they don’t seem to have cleavage or have any crystalline habits. They do appear amorphous as they break concoidally. The highly reflective metallic like material is probably what gives the particle magnetism. These black sand particles retain their magnetism for hours and whatever their composition they are soft. I interpret them to be a glass due to conchoidal fractures (Ralls). **The metal ruler on image top illustrates a 1 mm scale between black notches.**

Non magnetic samples from the structure. The Chert is mostly silica (cryptocrystalline quartz), the sandstone/siltstone of the Dothan sediments are mostly mid range Na-Ca type (Ralls).

References

[see – METEORITE]

Brent Dalrymple, Radiometric Dating Does Work! Reports of the National Center for Science Education