A bay ringed by active volcanoes where geothermal springs heat coastal waters. The collision of cold Pacific currents and volcanic heat creates microclimates where tropical species coexist with Arctic ones.
kuhnmi, CC BY 2.0, via Wikimedia Commons
A Cauldron on the Ring of Fire
Avacha Bay is a vast, 215-square-kilometer natural harbor on the southeast coast of the Kamchatka Peninsula. Its existence results from its location on the Pacific Ring of Fire, a zone of intense tectonic activity. Here, the Pacific Plate subducts, or slides, beneath the Eurasian Plate at a rate of about 80 millimeters per year. This geological process fuels the region's dynamic volcanism.
The bay is famously encircled by a trio of volcanoes. Koryaksky (3,456 meters), Avachinsky (2,741 meters), and the extinct Kozelsky volcano are north of the bay. Avachinsky is one of Kamchatka's most active volcanoes, with at least 17 recorded eruptions. One major eruption, between 30,000 and 40,000 years ago, caused a massive landslide that formed a horseshoe-shaped caldera and sent 500 square kilometers of debris south, forming the ground beneath the modern city of Petropavlovsk-Kamchatsky. The heat from the magma chambers deep beneath these volcanoes powers a network of geothermal springs, some of which vent directly into the bay, altering the local marine environment. Fumaroles near Avachinsky's summit emit gases measured at over 400°C.
An Unlikely Ecosystem
The waters of Avacha Bay have different temperatures. While the broader bay experiences frigid Pacific temperatures, sometimes dropping below -1°C in winter, the areas around hydrothermal vents create pockets of significantly warmer water. By the end of summer, surface waters may warm to 15°C, but at a depth of 10 meters, the temperature is a cold 7°C. This thermal gradient allows for a unique biological arrangement.
The ecosystem is a blend of typical subarctic species and organisms that thrive in warmer conditions. The seafloor hosts dense communities of sea urchins, anemones, sponges, and ascidians. Thickets of brown algae provide habitats for hairy crabs and, during spawning season, king crabs. The bay supports 32 species of fish, including salmon, cod, and flounder. This environment also attracts marine mammals like seals, sea lions, and sea otters. While "tropical" is an exaggeration, the geothermal heat supports robust populations of thermophilic, or heat-loving, bacteria. These chemosynthetic organisms form the base of the food web around the vents, converting chemicals into energy in the absence of sunlight, similar to ecosystems found at deep-sea "black smokers". This allows for a density and variety of life for these latitudes.
💡Fun Facts
Avacha Bay is one of the largest bays in the world, with a total area of 215 square kilometers, and is said to be large enough to fit the entire world's merchant fleet.
The city of Vilyuchinsk, on the bay's coast, is a closed military city that hosts Russia's largest nuclear submarine base.
The bay's entrance is guarded by a trio of tall, finger-like sea stacks called the "Three Brothers," which are a major local landmark.
Over 70 sunken ships, mostly from the Russian Navy, lie at the bottom of the bay.
The bay is a natural feature and is always accessible, though boat tours are subject to weather conditions and tour operator schedules.
Admission
Free to view from shore. Boat and wildlife tours must be booked and have associated costs.
Accessibility
The shoreline is accessible in and near the city of Petropavlovsk-Kamchatsky. Access to the most interesting geological and ecological sites is primarily by boat. The surrounding terrain is mountainous and volcanic.
