Tombstone Territorial Park, nestled in the heart of the Yukon, is a geological tapestry woven from the threads of volcanic activity, glaciation, and tectonic forces, resulting in a landscape of dramatic peaks, cirques, and permafrost features rarely seen elsewhere. Its unique combination of granitic plutons sculpted by ice and permanently frozen ground makes it a haven for scientists and a breathtaking spectacle for visitors.
The unique geology of Tombstone Territorial Park is the result of a complex interplay of geological processes spanning millions of years. The most prominent feature is the Tombstone Range, a collection of dramatic, jagged peaks formed from intrusive granitic plutons emplaced approximately 90 million years ago during the Cretaceous period. These plutons, essentially large masses of solidified magma deep within the Earth's crust, were subsequently exposed by erosion and sculpted by multiple periods of glaciation.
Glaciation played a pivotal role in shaping the landscape we see today. Massive ice sheets and alpine glaciers carved out deep U-shaped valleys, creating the iconic cirques (bowl-shaped depressions) that define the headwalls of many valleys. As the glaciers retreated, they left behind a legacy of moraines, ridges of unsorted sediment deposited along the glacier's edges and terminus. These moraines dammed valleys, creating numerous pristine lakes and ponds that dot the park.
The presence of permafrost, ground that remains frozen for at least two consecutive years, adds another layer of geological complexity. Permafrost significantly impacts the landscape through processes like thermokarst, the thawing of ice-rich permafrost leading to subsidence and the formation of irregular terrain. This is evident in features like pingos (ice-cored hills) and active layer detachment slides, where the surface layer of soil and vegetation slumps downslope.
The distinctive jagged peaks of the Tombstone Range are composed primarily of granite, a coarse-grained igneous rock rich in quartz, feldspar, and mica. The magma that formed these granites cooled slowly beneath the Earth's surface, allowing large crystals to develop. The subsequent uplift and erosion of the overlying rock exposed these granitic plutons, making them vulnerable to weathering and glaciation. The varying resistance of the granite to these processes resulted in the dramatic, irregular shapes that characterize the range.
The powerful forces of glaciation have left an indelible mark on Tombstone Territorial Park. The U-shaped valleys are a testament to the erosive power of glaciers, which widened and deepened existing valleys, transforming them from V-shaped stream valleys into broader, more rounded forms. Cirques, the bowl-shaped depressions at the head of valleys, are where glaciers originated and are often filled with meltwater lakes. Moraines, ridges of sediment deposited by glaciers, act as natural dams, creating many of the park's stunning lakes and wetlands.
Permafrost underlies much of Tombstone Territorial Park, playing a significant role in shaping the landscape and influencing ecological processes. The presence of permafrost restricts drainage, leading to the formation of waterlogged areas and contributing to the unique vegetation communities found in the park. Thermokarst features, such as pingos and thaw slumps, are visual reminders of the dynamic interaction between permafrost and the changing climate. The active layer, the surface layer of soil that thaws each summer, is particularly susceptible to erosion and instability.
FAQ 1: What is the age of the rocks in Tombstone Territorial Park?
The dominant granitic rocks of the Tombstone Range are approximately 90 million years old, dating back to the Cretaceous period. However, some sedimentary rocks found in the park are significantly older, dating back hundreds of millions of years.
FAQ 2: Are there any active volcanoes in Tombstone Territorial Park?
No, there are no active volcanoes in Tombstone Territorial Park. The volcanic activity that formed the granitic rocks occurred millions of years ago. The rocks are intrusive and have been exposed by uplift and erosion, which means they were formed deep underground.
FAQ 3: What causes the jagged appearance of the Tombstone peaks?
The jagged appearance is primarily due to the combined effects of weathering, erosion, and glaciation acting on the exposed granitic rocks. The differing resistance of the granite to these processes, along with the presence of fractures and joints, has resulted in the sharp, irregular shapes.
FAQ 4: What are pingos, and why are they found in Tombstone Park?
Pingos are ice-cored hills that form in permafrost regions. They are formed when water migrates to a freezing front beneath the surface and expands as it freezes, pushing up the overlying soil and vegetation. They are found in Tombstone Park because of the widespread presence of permafrost and the availability of water.
FAQ 5: How has glaciation affected the rivers and lakes in the park?
Glaciation has profoundly shaped the rivers and lakes in Tombstone Park. Glaciers carved out U-shaped valleys that now contain many of the park's rivers and lakes. Moraines deposited by glaciers have dammed valleys, creating numerous lakes. Glacial meltwater is also a primary source of water for many of the rivers and lakes.
FAQ 6: What is the active layer, and why is it important?
The active layer is the surface layer of soil that thaws each summer in permafrost regions. It is important because it is the zone of biological activity and plant growth. It is also susceptible to erosion and instability, and changes in the thickness of the active layer can have significant impacts on the landscape and ecosystem.
FAQ 7: Is there any evidence of past earthquakes in the park?
While there isn't substantial, readily available evidence documenting major seismic events within Tombstone Territorial Park itself, the region lies within a seismically active zone. The complex tectonic history of the area, including the uplift of the Tombstone Range, suggests the potential for past seismic activity. Detailed geological studies could potentially uncover evidence of past earthquakes in the form of fault lines or deformed rock formations.
FAQ 8: What types of rocks besides granite can be found in Tombstone Park?
While granite is the dominant rock type, other rock types can be found in Tombstone Park, including sedimentary rocks (such as shale and sandstone) and metamorphic rocks (such as gneiss and schist). These rocks represent different geological periods and processes.
FAQ 9: How does permafrost impact the infrastructure (e.g., trails, roads) in Tombstone Park?
Permafrost poses significant challenges to infrastructure in Tombstone Park. Thawing permafrost can cause ground subsidence, leading to damage to trails, roads, and other structures. Special engineering techniques, such as using insulated foundations, are often necessary to mitigate the impacts of permafrost thaw.
FAQ 10: Are there any fossils found in Tombstone Territorial Park?
While Tombstone Park is not particularly known for its fossil record, given the presence of sedimentary rocks, there's potential for discovering fossils. Fossil finds would likely be related to marine environments, reflecting the area's geological history when it was submerged under shallow seas.
FAQ 11: What kind of erosion features are most common in the park?
The most common erosion features are those related to glaciation, freeze-thaw cycles, and fluvial (river) action. These include cirques, U-shaped valleys, moraines, talus slopes (accumulations of rock debris at the base of cliffs), and river channels. Wind erosion also plays a role, particularly in exposed areas.
FAQ 12: How is climate change affecting the geological features of Tombstone Park?
Climate change is having a significant impact on the geological features of Tombstone Park, primarily through permafrost thaw. As temperatures rise, permafrost is thawing at an accelerated rate, leading to ground subsidence, increased erosion, and changes in drainage patterns. This can destabilize slopes, damage infrastructure, and alter ecosystems. Furthermore, changing precipitation patterns could alter the rate of glacial melt and fluvial erosion.