It’s no ordinary rock, according to Edwin Nissen, professor of ocean and earth sciences at the University of Victoria. It likely traveled – via glacier – hundreds of kilometers from the Coast Mountains north of Vancouver between 10,000 and 20,000 years ago. Nissen said the technical term is a glacial erratic — basically a rock out of place — in this case, an igneous rock from the mainland transported by glacial movement. During the Pleistocene epoch, which ended about 12,000 years ago, huge glaciers flowed from the coast mountains, over Vancouver Island and into the Pacific Ocean. The continued flow of the glacier would have torn rocks and transported them to the ice, eventually depositing them randomly as the glacier melted as the Great Ice Age came to an end. Igneous rocks, formed from magma, are not commonly found on Vancouver Island’s coastline, Nissen said. Here, there are volcanic rocks formed on the sea floor and softer, metamorphic rocks formed from sediments, often closer to land. Crystallized igneous rock is not the only reminder of historic glaciers along the region’s coasts. Nissen notes that glacial striations—basically, scratch marks left by hard igneous rock along softer rock—reveal the flow of ice from north to south. “When you have hard rock scraping over soft rock, the hard rock will create these really deep grooves in the softer rock,” he said. “It’s not necessarily a low-tide issue – you can actually see them at any time. But they may be more exposed than the ebb.” The marks are indications of an ancient era, but speaking of, the geological wonder represents only a blip in Earth’s timeline, Nissen said. “Twenty thousand years ago or 10,000 years ago, every time these glaciers flowed and retreated, it’s a blink of an eye in geological terms,” he said. “The earth is 4.5 billion years old, and many of the rocks we see here are tens or hundreds of millions of years old.” While visible at normal tides, the alien rocks and glacial ridges are now fully revealed due to an unusually low tide, a phenomenon caused by the high summer solstice sun aligning with a full moon closer to Earth’s orbit, which also called perigee moon. The tide has receded about 20 to 25 centimeters below an average low tide line, said Richard Dewey, deputy director of science at Ocean Networks Canada. The last full moon in June brought a similar ebb. “They are rare but not unexpected,” Dewey said. “They often come together at this time of year and especially during the summer solstice.” The effects also create a long tidal cycle, he said. “We often think that high tide and low tide were about six hours apart, but on Wednesday, we had a very high tide at midnight and high tide at midnight.” The next major low tide event is expected in mid-June 2026. With the sun and moon in full force on BC’s south coast, the normally underwater worlds of vegetation, shellfish, crabs and other intertidal species are also exposed to the sun. The adaptive littoral habitat is diverse and abundant, oscillating between exposure and submergence. “This habitat that is exposed at these very low tides is really not that far away,” Dewey said. “It’s 30 to 40 meters offshore on a sloping beach … It’s there all the time, but we can see it in the air during these low tides.” Dewey said low tides are only a concern if they line up with heat domes like the one that hit B.C. “If we have more heat domes, they will occur during the summer solstice when we see the lowest tides,” Dewey said. “The combination of those is something to watch out for.” Those who want to explore the irregular glaciers or check for intertidal species during low tide should do so, but with caution, Dewey said. “We want to be passive observers and not add additional stress to these systems that are experiencing these low tides,” he said. “The last thing they need is for us to come and bother them even more. “Look and explore, but try not to disturb.” [email protected]
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