Two Brothers (islands, Dalnegorsk)

Kekury Two Brothers is a geological monument, a classic example from a whole class of similar exogenous relief forms. The background of the rock origin dates back to the Upper Cretaceous - the Lower Paleogene, the era of intense volcanism and the formation of structures of the East Sikhote-Alin volcanic belt. In this era, about 60 million years ago, on the outskirts of the Eurasian plate in the area of ​​the future Primorsky Territory, active volcanic processes took place, and the thickness of the loose pyroclastic material of acidic effusives accumulated. In the centers of some volcanic buildings, along magma-leading channels, a more viscous lava was introduced and solidified in them. Thus, the necchi (or vents) were formed. ^[2] In the following millions of years, during the Paleogene and most of the Neogene, lithification (compaction) of the effusive strata took place. However, their density and mechanical strength remains low compared to the rocks of which some are composed. About 16 million years ago, the formation of the depression of the Sea of ​​Japan began. ^[3] With a gradual increase in the area of ​​the sea basin, coastal abrasion activity also increased, and a shelf began to form. In the era of climatic optima and related marine transgressions, sea levels rose and the front of abrasion moved far to the west, destroying and re-laying off the coastal rocks of different ages on the shelf. Due to the vertical movements of the earth's crust, in conjunction with fluctuations in sea level, the erosive section of rocks of the coast was carried out at various levels. Perhaps several hundred thousand years ago, in the era of high and prolonged marine transgressions, the rocks of the necca of the Two Brothers were already “cut off” in their upper part by the abrasive effect of the sea. At the same time, a sea terrace could have been formed (west of the Neck) with an erosive front that went deep into the mainland.

Given the slow vertical movements of the coast and the complete correlation of the solar insolation plots with the sea level position, it is possible to approximately characterize the stages of coastline development. ^{[4] The} current stage of activation of coastal processes that determined the current appearance of the Two Brothers began about 135 thousand years ago. For approximately 20 thousand years, the sea level was higher than the present, reaching a maximum mark exceeding the sea level of the Holocene optimum by several meters. Nekka rocks were exposed in a cliff and the sea began to separate them from the main mass of rhyolite tuffs. Then, between 115 and 105 thousand years ago, a sharp drop in temperatures followed and, as a result, marine regression to a level of approx. −9 m to the modern. Immediately behind it, between 105 and 70 thousand years BC. e. two short waves of transgression +5 +6 m passed, separated by a short decline of no more than −2 m. These rises and lowerings of the sea level went very quickly, and the abrasive effect of the surf was “smeared” over a considerable vertical section of a steep coast. At the same time, Cape Briner may have become an island, and the lakes Vaskovsky and Zerkalnoye became sea bays, but they were not for long. The Nekk of the Two Brothers, before the start of the second stage of “processing” about 65 thousand years ago, was very similar to the modern Klokovskoe vent, located 1.2 km north of the bays. Klokovo. It was located on the eastern tip of a small peninsula and was a rock not yet divided, but already losing its integrity. The rock towered above the level of the ancient abrasion terrace. In its southwestern part, a deep grotto formed along the tectonic fault.

The interglacial period 65–35 thousand years ago, and the associated marine transgression, differed from the previous ones in their long duration and stability of the sea level position. And although the level rise was not high +2 +3 m, significant changes occurred in the coastal landscapes. The Rudnaya River managed to block the Vaskovskaya and Zerkalnaya bays with its sediments, making them lagoon lakes, and Briner Island was connected to the mainland by an alluvial spit. The Nekk of the Two Brothers separated from the mainland and became a kekur, connected to a rocky cliff at the beginning of a narrow rocky beach. The grotto in its southwestern part turned into a through arch. For tens of thousands of years, the peninsula, once attached to the nekku, retreated west by 80 - 100 meters. At the level of its cut, an extensive bench was formed - an underwater abrasion terrace. It is likely that in the wave shadow behind the kekur there was a pebble spit connecting it to the beach. Gradually, the kekur collapsed, the arches of the arch became higher and higher, until they completely collapsed.

In the preceding last Holocene transgression ice age, approx. 20-25 thousand years ago, the Kekurs were tall rocky ridges stretched from the south-west to north-east. Due to the lowered sea level, the near Kekur stood on the shore. The strait between the kekuras continued to deepen and expand. The distant ridge consisted of two or three protrusions of different heights.

The last Holocene transgression lasted from 10 to 4 millennium BC. e. Sea level rose to +4 +5 m, but due to the rapid rise and fall, significant changes in coastal landscapes did not occur. High coastal cliffs south of the Two Brothers practically did not collapse, only the low ancient terrace receded into the mainland another fifty meters. Two Brothers at this time were separated from the coast by a deep strait. The edges of the ridges were destroyed by storm waves more intensively than the central parts, and gradually the kekurs acquired modern outlines.

Currently, general cooling and falling sea levels are continuing, complicated by short-term (several hundred years) peaks of warming. According to Milankovitch’s cycles, a significant cooling on Earth will occur in about 50 thousand years. Over the next 40 thousand years, sharp temperature fluctuations are not expected. This means that the ocean level will fluctuate with a small amplitude near the current position (without taking into account the influence of vertical movements of the earth's crust). With the position of the erosion section close to the existing one, over a period of 40 thousand years, one can expect the retreat of high cliffs (cliffs) by several meters in areas of mountainous coasts, and by several tens of meters where coastal cliffs are low (cape opposite the Two Brothers, the coast north of Lidovka). The width and area of ​​benches (rocky underwater shoals) will increase, the Two Brothers kekurs will turn into ridges of low reefs, and the Klokovsky nekk will separate from the coastal massif and become a separate kekur. In the more distant future, after a few hundred thousand or a million years, with a combination of favorable factors, it is possible that a new kekur from a nekk of the Two Brothers may form at a lower level of erosion cut.

Due to the very small area and relatively high height, only abrasion processes are manifested on the islands. If on the small islands of the Amur Bay , such as Fake , Kamen Matveeva and others, comparable in size to the Two Brothers, you can still find relatively flat areas overgrown with grass and shrubs, only bare rocks are common here. This is due to the location of the Kekurs off the coast of the open part of the Sea of ​​Japan and, as a result, to the more intense exposure to waves. In addition, the morphology of the rocks plays a role. The kekur near the shore from the water edge to a height of about 15 m has very steep slopes - 75–90 °, sometimes up to 100 ° (negative slopes). On the distant kekur, up to about half its height (about 10 m) there are small areas, but the upper half is almost vertical. During storms, the prevailing wind and wave directions are from the south and southeast. The splash height of the spray of sea water can reach 12-16 m. During winter storms, the rocks are covered with ice crust. From these directions - south, southeast, east, the surface of the islands is lifeless. In the upper parts of the Kekurs, the appearance of vegetation is prevented by bird droppings. Plants can be found on slopes not affected by storms, but below the resting areas of seabirds. First of all, bright yellow, yellow-brown crusts of lichens are striking. They are common in the middle and upper belt of the Kekurs, on almost steep rock sections of the western - northeastern expositions. On the northwestern slope of the near Kekur, at heights of 14-18 m, in small pockets of rocks filled with soil, small groups of wheatgrass and low wormwood grow. The area of ​​the site with the most lush and diverse vegetation on all islands is 10-12 m ² . It is located on the northwestern slope of the distant Kekur facing the mainland, at an altitude of 5-8 m above the water edge. Here, on an inclined platform, limited by steep cliffs, mokret, wheatgrass, sedge and even horse sorrel grow. In summer, the site is distinguished by a bright green spot on the dark gray surface of the kekur and is clearly visible from the shore.

Probably the first to mention the Two Brothers V.K. Arseniev at the very beginning of the XX century. He made their first photos.

To the south of Cape Briner, two hundred meters from the coast, two more rocks stick out of the water, called, as always, “Brother and Sister”. It used to be a coastal gate. Their arch collapsed, and only one pillar remained. If you look at Cape Briner from the northern shore of Tetyukh Bay, then it seems that these posts are on a sandy isthmus.

- Arseniev V.K. “ Across the Ussuri Territory ”

In 1909, Sergey Dyukin took photographs of the kekuras, who explored the valley of the Tetyukhe River ( Rudnaya ) with his brother and sister this year. Gradually, the cliffs of Two Brothers became the "calling card" of Tetyuhe-Pristan, and then of the Dalnegorsky district and Northern Primorye. Their images are found in illustrated publications devoted to the nature of Primorye and the Far East both in the Soviet period and in subsequent years. In addition, the rocks of the Two Brothers on the background of the lighthouse of Cape Briner were depicted on a 1000-ruble banknote of the 1995 model.

Due to its convenient location near Rudnaya Pristan and Dalnegorsk, the coastal area in the area of ​​Cape Briner and Kekury Dvu Brothers is one of the most visited on the territory of the Dalnegorsky urban district. It should be noted that there is no descent to the beach for cars, the beach itself is rocky, in some places pebbly, and the bottom is rocky, uncomfortable for swimming. The coast of the Sea of ​​Japan near the Two Brothers is primarily interesting for diving and eco-tourism.

The nearest kekura can be wade. The distant one is separated by a deep strait and can be reached by swimming or by boat. There is a small grotto on the distant kekur. At the northern end there is a narrow crevice flooded by the sea. On the south side of the kekura there is a small pond of sea water, fenced off from the sea by rocks, which is filled with waves and splashes of breaking waves. Kekuras are composed of very strong rock, with sharp chips on the edges.