Integrative Natural History of Minnesota's North Shore, Part 19: Roots in Billion-year Lava | Gooseberry Falls State Park
Taken on the western side of the park's Middle Falls.
What happens when you're an Arbor Vitae (Thuja occidentalis) and you sprout on bare bedrock instead of real soil? Your roots get aggressive and go on a water- and nutrient-seeking expedition.
The rock here is basalt of the late-Mesoproterozoic North Shore Volcanic Group. It erupted about 1.1 Ga ago as part of the cataclysmic Midcontinent Rift event that almost tore North America apart.
The basalt is highly jointed. Joints are fractures in bedrock where there has been no appreciable shift in position on either side of the fissure. They often form when a section of the Earth's crust long confined by overlying rock units is finally exposed at the surface through the process of erosion. Relieved of all that former topweight and confining pressure, it stretches vertically, shrinks horizontally, and cracks.
Plant roots often exploit joints by growing down into them. And as they slowly expand they can exert so much pressure on the stone that it fractures even more.
To see the other photos and descriptions of this series, visit
my Integrative Natural History of Minnesota's North Shore album.
Integrative Natural History of Minnesota's North Shore, Part 19: Roots in Billion-year Lava | Gooseberry Falls State Park
Taken on the western side of the park's Middle Falls.
What happens when you're an Arbor Vitae (Thuja occidentalis) and you sprout on bare bedrock instead of real soil? Your roots get aggressive and go on a water- and nutrient-seeking expedition.
The rock here is basalt of the late-Mesoproterozoic North Shore Volcanic Group. It erupted about 1.1 Ga ago as part of the cataclysmic Midcontinent Rift event that almost tore North America apart.
The basalt is highly jointed. Joints are fractures in bedrock where there has been no appreciable shift in position on either side of the fissure. They often form when a section of the Earth's crust long confined by overlying rock units is finally exposed at the surface through the process of erosion. Relieved of all that former topweight and confining pressure, it stretches vertically, shrinks horizontally, and cracks.
Plant roots often exploit joints by growing down into them. And as they slowly expand they can exert so much pressure on the stone that it fractures even more.
To see the other photos and descriptions of this series, visit
my Integrative Natural History of Minnesota's North Shore album.