What major event distinguishes the end of the Hesperian Period?

The end of the Hesperian Period on Mars is marked by a significant geological transformation characterized by resurfacing processes, particularly through lava flows. During this period, volcanic activity played a crucial role in shaping the Martian landscape. The flood basalt and volcanic plains created by these lava flows contributed to the extensive modification of the planet's surface, burying older geological features and creating new landforms.

Lava flows are particularly notable because they indicate active geological processes that were prominent at this time, suggesting a more dynamic environment on Mars compared to earlier periods. The resurfacing efforts also reflect a transition in the planet's geological history, leading into the much-quieter Amazonian Period that follows the Hesperian. This significant volcanic activity is what truly distinguishes the closing of the Hesperian Period, setting the context for the ongoing study of Martian geology and its evolution.