Question

The following passage is adapted from an article on early twentieth-century scientific expeditions:

In March 1927, Russian mineralogist Leonid Kulik set out on the first systematic field expedition to investigate the catastrophic explosion that had devastated central Siberia nearly nineteen years earlier. On June 30, 1908, a mysterious atmospheric detonation over the Podkamennaya Tunguska River basin had flattened thousands of square kilometers of dense taiga. Yet, owing to the extreme remoteness of the region and the political turmoil of the Russian Civil War, no physical survey of the site had been undertaken. Having secured a modest allocation of 1,500 rubles from the Soviet Academy of Sciences following his 1921 preliminary survey of Siberian meteorite reports, Kulik established an operational base at the isolated Vanavara trading post. From Vanavara, Kulik and his team traveled northward across frozen bogs and dense forests using reindeer sleds provided by local Evenki hunters.

Upon reaching the inner perimeter of the devastation near the Makirta River in mid-April, Kulik made an unexpected observation regarding the structural condition of the forest. Scientists had anticipated that a massive surface impact would have uprooted trees uniformly in a radial direction from the central point. However, as the expedition traversed the outer region—where millions of larch and pine trees lay prone on the ground, pointing symmetrically outward—they eventually arrived at a broad depression known locally as the 'Great Cauldron.' Here, at the precise center of the blast area, the pattern of forest damage altered dramatically. Instead of being uprooted, the trees at the immediate epicenter remained standing fully erect. Their branches, twigs, and bark had been completely stripped away by intense heat and shockwaves, leaving thousands of bare, scorched trunks upright like a forest of stark telegraph poles across a twenty-kilometer radius.

Kulik recognized that this peculiar configuration of standing, branchless timber provided vital physical evidence regarding the nature of the event. The vertical alignment of the trunks indicated that the explosive shockwave had struck the ground from directly above, propagating downward at a perpendicular angle rather than laterally across the terrain. This observation led Kulik to hypothesize that the object had not struck the Earth's surface as a solid mass, but had instead detonated violently in the upper atmosphere.

Despite this breakthrough, Kulik remained determined to locate solid physical remnants of the object. He focused his search on several marshy depressions within the epicenter, most notably a peat bog dubbed the Suslov funnel. Kulik suspected that these depressions represented impact craters created by a fragmented iron meteorite. Armed with hand-operated drills and spades, the expedition spent months excavating the frozen mud of the Suslov funnel during the summer thaw of 1927. However, the labor yielded no nickel-iron meteoritic fragments, nor did it reveal any underlying impact crater structure. Subsequent analysis confirmed that the Suslov funnel was merely a natural thermokarst formation produced by the melting of permafrost. Although Kulik returned to Moscow without the physical extraterrestrial specimens he sought, his meticulous mapping of the epicenter's erect, scorched timber established the foundational scientific understanding of high-altitude atmospheric airbursts.

Based on the passage, what did Leonid Kulik observe regarding the condition of the trees situated at the immediate epicenter of the blast during his 1927 expedition?