The Beehive and The Bowl
Figure 1. Map of Mount Desert Island.
The red circle shows where the Beehive is located.
Credit: Greg A. Hartford
The Beehive is considered to be a classic roche moutonnée as it has a gradual slope to the north and a steep cliff to the south (Figure 2). This is due to the movement of the Laurentide Ice Sheet that covered Canada and the northern United States. The ice sheet formed about 25,000 years ago and lasted until about 14,000 years ago (Gilman et al 1988). The ice sheet moved from the north to the south. As the ice sheet went over the Beehive, it eroded and smoothed the north side. When passing over the south side, the meltwater seeped into the cracks and refroze. As the ice sheet continued to move south, it plucked the rocks, creating a jagged steep cliff.
The Bowl was also created by the ice sheet as its weight created a depression on the lithosphere. Once the ice sheet melted, the depression then filled with water, creating a pond (Figure 3).
The Beehive is a 520-foot mountain in Acadia National Park. It is located to the southeast of Mount Desert Island, across from Sand Beach (Figure 1). The peak of the mountain provides spectacular views of Sand Beach and Great Head. The trail to the peak of Beehive is considered strenuous as it is steep. To provide support, there are several handrails and iron rung ladders along the trail. The Bowl is a glacially created pond that is located about .5 miles to the northwest of Beehive. A trail can be taken directly from the Beehive to the Bowl.
Figure 2. Beehive. Gradual north slope and steep south side.
Credit: Marnie McInnes
Figure 3. View of the Bowl.
Credit: Harry Horn via AllTrails.com
The Beehive is made up of Cadillac Mountain Granite (Figure 4 and 5). The granite is a coarse-grained rock that formed intrusively. It contains bits of pink or gray feldspar, white quartz, and black hornblende. Cadillac Mountain Granite is surrounded by the Shatter Zone. The Shatter Zone consists of angular rocks such as Ellsworth Schist and Bar Harbor Formation. The Shatter Zone is thought to have been the edges of a volcano that collapsed. The central area was then intruded by magma and became the Cadillac Mountain Granite (Gilman et al 1988).
Figure 4. Cadillac Mountain Granite with lichen
There are many crescentic fractures that can be seen at the top of Beehive (Figure 6). These were created by the ice sheet as it chipped the rock when it moved over. The orientation of the crescentic fracture that we measured had an orientation of 163°.
There were also many fractures present on the top of Beehive. We measured two sets of fractures with four measurements in each (Figure 7,8,9 and Table 1). The averages of the fractures showed that a set runs from the northwest to the southeast and the second set runs from the northeast to the southwest.
Figure 5. Bedrock Geology of The Beehive and The Bowl.
Modified after Gilman and Chapman, 1988
Figure 6. Crescentic fractures on the top of Beehive shown with a north-south orientation. (163 degrees S)
Figure 7. Fractures measured for Set 1.
Table 1
Figure 8. Fractures measured for Set 2.
Figure 9. Visual Orientation of Fractures
On the trail to the Bowl, we saw a quartz vein that had an orientation of 356°. (Figure 11 and 12).
Figure 11. Quartz Vein (oriented 356 degrees N)
Figure 12. Close up of Quartz Vein.
The Bowl is also made up of Cadillac Mountain Granite. Glacial till can be found to the north and south of the pond (Figure 13 and 14). Glacial till is considered to be poorly sorted sediments as they range from clay sized to small pebbles. The sediments were created when the glaciers added friction and eroded the rocks as they moved across. The sediments were then dragged by the glacier until it finally reached the ocean and deposited. We can then see till around the Bowl as well as in other areas such as Sand Beach, due to sea levels falling and revealing this marine clay. Figure 13 displays till to the north and south of the Bowl, similar to the movement of the glacier. Plants and trees that grow in these areas can be seen sliding down slowly over time as the till does not offer much support.
Figure 13. Geological Map of the Beehive and the Bowl. The legend shows that the bedrock is Cadillac Mountain Granite, there is till to the north and south of the Bowl, and the dots display where crescentic fractures were observed.
Figure 14. Glacial Till by The Bowl.
Gilman, R., C. Chapman, T. Lowell, and H. Borns. 1988. The Geology of Mount Desert Island. Maine Geological Survey, Department of Conservation.
David Ullman. 2016. The retreat chronology of the Laurentide Ice Sheet during the last 10,000 years and implications for deglacial sea-level rise. University of Wisconsin-Madison, Department of Geoscience.
References
Created By: Coral Matos'20 and Connar Shea Foote'21