Kellys Mountain is located in Cape Breton, Nova Scotia along route 105 of the Trans Canada Highway. The mountain is known for its steep slopes and scenic lookouts over Bras d’Or with views of Seal Island Bridge, Great Bras d’Or channel and Boularderie island. There is a sharp hairpin turn at the foot of the eastern end of the mountain that provides switchbacks and a steep 180 degree descent.
The mountain sits on a peninsula of land surrounded on three sides by water with Great Bras d’Or to the south, Cabot Staite to the east and St. Anns Bay to the north.
Kellys Mountain consists of Kellys Mountain granite from the Late Cambrian period, and Kellys Moutain Gneiss. Smaller deposits of Kellys Moutain dioritic rocks can be found to the southwest and north east.
Granite is an intrusive rock, the most common type of rock in the earth’s continental crust. It is composed minerals which can vary depending on the location it was formed.
Feldspar: This is the most common mineral found in granite, accounting for up to 60% of the rock’s composition. The two main types of feldspar found in granite are orthoclase and plagioclase.
Quartz: Quartz is another common mineral found in granite, accounting for up to 30% of the rock’s composition. It is a hard and durable mineral that gives granite its characteristic toughness.
Mica: Mica is a mineral that is commonly found in granite, accounting for up to 10% of the rock’s composition. It is a shiny and reflective mineral that gives granite its characteristic sparkle.
Hornblende: Hornblende is a dark-colored mineral that is sometimes found in granite, accounting for up to 5% of the rock’s composition. It is a hard and durable mineral that can give granite a darker color.
Biotite: Biotite is another dark-colored mineral that is sometimes found in granite, accounting for up to 5% of the rock’s composition. It is a type of mica that gives granite a dark, almost black color.
Granite comes in various colours, most commonly pink, white and variations of gray and black. It is important to note that granite must contain 20% quartz so most black granite is likely gabbro and not granite.
Kellys Mountain Granite
Weathering of Granite
Unlike other types of rock, in particular sedimentary rock which weathers more easily, granite is very resistant to weathering as it is an intrusive rock and hard for water to penetrate, however all rocks are affected by weathering depending on exposure and location.
Types of granite weathering
- Cooling
Granite cools slowly within the Earth’s crust. Feldspar, quartz and mica crystals form during the cooling. Vertical and horizontal fissures form within the rock mass as it contracts. The fissures expand to larger fractures as the rock cools further.
- Wind
Wind, water and ice denude the soil and Earth’s crust overlying the granite mass, exposing it to the atmosphere. The rock expands and contracts in reaction to changes in temperature. It shatters on the surface and the fractures widen to form crevices.
- Hydrolysis (Chemical weathering)
Hydrolysis is the chemical weathering of minerals by a mildly acidic water that forms when rains dissolve trace gases in the atmosphere.
- Salt
Salt weather can affect the properties of granite and reduce its durability
- Frost
Granite has natural cracks which can expand and contract at extreme temperatures. As these cracks expand, physical weathering can occur
What causes granite to decompose?
Biotite is a particularly active agent in the weathering process of granite. It expands to form hydro- biotite that helps disintegrate the rock into grus ( the accumulation of angular, coarse grained fragments). The feldspars break down by hydrolysis and hydration into clays and colloids, which may migrate from the rock.
Logging Requirements
- Please send your answers before logging this earthcache
- If you are in a group, only one member needs to submit the answers however each person will need to post a photo showing they were on site. A group shot is acceptable.
- Logs without sending answers will be deleted
Parking is available at the posted coordinates. You do not need to enter the KOA campground to make your observations.
Questions:
- Estimate the height of the granite rock face?
- What evidence to you see that the granite wall has suffered weathering
- Based on the write-up, what types of granite weathering is likely a factor at this location
- Do you see evidence that water plays a significant role in weathering of this granite or is it one of many factors that play a role? ( Hint: is there regular and direct exposure to water or indirect exposure through rainfall and storms)
- Is it safe to stand at the bottom of the rock face
- MANDATORY: Take a photo of you or your party. Your face does not have to be in the photo. A thumbs up, your caching name or a personal item is acceptable. Do not show the height of the granite slope. Post your photo in your found log.
References:
https://www.researchgate.net/figure/The-geology-of-Kellys-Mountain-and-Big-Hill-Cape-Breton-Island-Nova-Scotia-with_fig2_318714812
