AP-Gorges

DLESE Fingerlakes
For best viewing results, set the elevation exageration to 2 or 3.
Open this answer sheet to use as you work through the stops in this activity.

Cascadilla and Fall Creeks

Stop 1.1 - Ithaca and Cornell University's Campus
The western side of Cornell's Campus is bounded by a steep slope running down into the city of Ithaca. The south side of the campus is bounded by Cascadilla Creek. North is bounded by Fall Creek.
The two creeks (Cascadilla and Fall) carve deep gorges into the local bedrock. For some time, the timing of the formation of these gorges was uncertain. It appears now that the gorges preexisted the most recent period of glaciation and were deepened during the melting.
The steep hill running from Cornell's campus into Ithaca marks the edge of a larger pro-glacial lake. Before the last glaciation of NYS, lakes and rivers in this region drained towards the south into what is now the Susquahana drainage basin. The glaciers in this area created moraine dams near the southern end of Cayuga Lake. Subsequent to the melting of the glaciers, rivers and lakes in this area now drain north through the St. Lawrence drainage basin. This past shoreline can be seen as a steep slope almost the entire distance around Lake Cayuga.
1. What was the approximate elevation of "Glacial Lake Cayuga's shoreline?
2. How much has the water level dropped in Cayuga Lake since the glaciers melted?

Stop 1.2 - Beebe Lake
Read about the geology and geologic history of the fingerlakes region in part 1 of this report.
Ithaca is Gorges; Part 1 (pdf)
Thanks to Alex Moore, Cornell University.
3. According to the topographic map overlay (and the map on pg. 2 of the pdf), what evidence exists that suggests the meandering stream flowing into Beebe lake were not entirely carved AFTER the last glaciation? (hint: think rates of weathering).

Stop 1.3 - Cascadilla Field Trip
Follow along on this field trip through Cascadilla Gorge.
Topics will include:
- Ripple Marks
- Fossils
- Kimberlite Dikes
- Plunge Pools at the base of water falls.
Thanks to Alex Moore, Cornell University.
4. What do ripple marks preserved in the sedimentary rocks of this region indicate?
5.How do the fossils preserved in the bedrock of this gorge support your previous answer?

Snee Hall
Snee Hall is home of the Cornell geology department.
The atrium of the building.
The seismic recording station behind the glass doors.
Shamless plug for the Cornell geology department :)

View SW from the roof
The image below shows the view towards the south west from the roof of Snee Hall. The landscape of this region is characterized by the low rolling hills and deep gorges carved into the mostly horizontal Devonian-aged bedrock.

Enfield Glen

Enfield Glen 1

Enfield Glen 2

Stop 2.1 - Enfield Glen
Read about the geology and the history of Enfield Glen in this report.
Ithaca is Gorges; Part 2 (pdf)
Thanks to Alex Moore, Cornell.
6. The walls of Enfield Glen are nearly vertical and the stream bed is nearly horizontal, creating a box-shaped river valley rather than the traditional ‘V’-shaped river valley or ‘U’-shaped glacial valley. What helps control the relatively unique river valley shape in this region?

Stop 2.2 - Enfield Glen Field Trip
Follow along with this field trip to Enfield Glen.
Topics covered include:
- Interbedded shale ans siltstone
- Sole marks as paleocurrent indicators
- Joint directions and their control on the stream path.
Thanks to Alex Moore, Cornell University.
7. Close inspection of the gorge cliffs reveals that they are comprised of interbedded shale and sandstone. What environment is most likely responsible for their deposition?
8. Further inspection of the gorge cliffs shows that the sandstone and shale are not uniformly weathering. Which type of rock weathers more easily and why?
9. The river through Enfield Glen makes sharp, 90° turns. This is atypical for most river systems. What (think about question 6) controls the direction of stream flow here?

Ludlowville and Taughannock Falls

Ludlowville

Taughannock

Stop 3.1 - Ludlowville Falls
The cap rock of this waterfall is the more resistant Tully Limestone. The weaker Morrisville shale underlies the Tully, and can be seen to be undercutting the cap rock. This will ultimately cause headward erosion as the falls continue to break off and retreat towards the head of the river.
Compare the elevation of the falls (Tully LS) on the eastern side of Lake Cayuga to the elevation of the outflow of Taughannock Creek on the west side. Both are composed of the Tully LS.
10. Why does the Tully Limestone create the top of the falls in this location? What factor about the Moscow Shale allows it to undercut the Tully Limestone?
11. In what direction will the falls move in the future (add a sketch if necessary)? Why?
12. What is the elevation of the Tully Limestone near Ludlowville Falls? (just upstream from the falls).
Photo by Steve Kluge

Stop 3.2 - Bedrock Geology
The cap rock of Taughannock Falls is the more resistant Sherburne Fm (sandstone). The sloping walls of the gorge are made of the weaker Genesseo Shale. The Tully Limestnone makes up the bottom of the gorge valley.
13. What is the elevation of the Tully Limestone near Ludlowville Falls (where the river flows into the lake).
14. What is the difference in elevation of the Tully Limestone between the east and west sides of Cayuga Lake? Refer back to question 12 above)
15. In the box on your answer sheet, sketch how the bedrock in central New York will be dipping based on the elevation of the top of the Tully Limestone.
Click here to see the answer
Photo by Steve Kluge

Stop 3.3 - After the Storm
This image was taken by Bill Hetch on April 5, 2005. A significant rain event in the area took place during April 3-4
Use the data here to create a two-line graph of precipitation and stream flow.
16. What is the relationship between stream flow and precipitation?
17. Why is there a delay between a storm and a rise in the stream discharge?
18. There was a minor rain event on March 24, 2005 (0.43 inches of rain). What happens to stream discharge due to this rain event?
19. Why might the response to this rain event (3/24) have been different than the rain events on March 28 and April 2, 2005?