This urban geotour is a short trek up and over the top Halifax Citadel National Historic Site – traversing the 30 meter high drumlin, a pile of gravel, sand and rocks, dropped here by a melting glacier 15,000 years ago. At the bottom of the drumlin, along the edge next to Citadel High School, you can see grooves carved into the surface of the underlying slate bedrock (Halifax Formation, 560 mya). The grooves trace the direction the glaciers moved, as an the immense ice layer more than one kilometer thick scraped across the landscape.
A drumlin is a hill of sediment that has been streamlined by glacial flow causing an elongate, tear drop shape.
Accessibility and Cautions
- This walk does involve a walking ascent and decent of more than 30 m with the route on sidewalk, walking paths or grass field.
- While walking around the Halifax Citadel features well maintained sidewalks, care should be taken with traffic along the roads. Use typical caution as you would in an busy urban downtown core.
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Notes and Stops
The tour starts at the Museum of Natural History.
Stop #1 – Did you know? In front of the Museum of Natural History the concrete sidewalk has two paw prints of a wolf.
Walking toward Citadel Hill, cross the street at the crosswalk, and then cross the other intersection to walk along Bell Road.
Stop #2 – On December 6, 1917, Mont-Blanc’s main cargo was bulk high explosives. When barrels of petrochemical on deck triggered the blast, the ship was transformed into a three-kiloton bomb in a busy modern port.
Stop #3 – A small British Survey marker with an arrow is made of granite. The granite was likely sourced from a quarry near Peggy’s Cove, and brought to Halifax Harbour aboard a British Ship. The arrow and initials would be noted on survey maps when the British were establishing Halifax.
Stop #4 – An urban trace “fossil” of a leaf can be seen in the concrete sidewalk. Concrete is an important material in urban environments, used for sidewalks, bridges, and building foundations. It is made with aggregate (pebbles), sand, cement, water and air. The leaf “fossil” represents a small moment in time, perhaps a four hour period, when the concrete was still wet and curing.
From this location, we can look up and see the shape of the Citadel drumlin. The scene would have looked much different 15,000 years ago, when 1-2 km of ice was above the location, melting and depositing this large pile of sand, gravel and boulders. As the ice melted and retreated more northerly, the drumlin was left behind.
Stop #5 – The gatepost at Halifax Citadel, is composed of grey quartzite, a metamorphic rock that is commonly used as a building stone and aggregate in the Halifax area. The top of the gate post is made of granite, like the type you saw at the British Survey marker.
Climb the Drumlin
As we walk up the drumlin, feel the challenge of climbing up the 30 meter elevation. Look around and see the views of the surrounding area. Imagine what the area was like thousands of years ago.
If you were looking out at the harbour 12,000 years ago, there was no sea water. This was a lowland river valley and the ocean coastline was 20 km off the current headlands. About 6,000 years ago the sea level rose to fill the outer harbour and also flooded into the Bedford Basin.
Stop #6 – At the top of the drumlin, you can look into the Halifax Citadel to see the deep moat and stone wall. These rock walls were built in 1856, the fourth version of the Fort. Earlier wood versions had been built in 1749, 1770, and 1796. During these constructions, the height of the drumlin was lowered by 17 meters. The third Citadel was built with the effort of the Maroons.
Learn more about the history of Halifax Citadel National Historic Site.
As you climb down the northern side of the drumlin, you can look out over the Halifax Common, see the Oval and sports fields.
Stop #7 – Another British Survey marker made of granite can be seen near the tree at the corner. This is a large survey marker, but made of the same granite and likely from Peggy’s Cover area.
Stop #8 – The highlight of this urban geotour, are the glacial striations that are visible in the field. The grooves in the slate bedrock were carved by the glacier when it was still very thick and moving south-west direction 20,000 years ago. The 2 km thick glacier pushed boulders across the bedrock, carving the deep grooves and creating a smooth flat plane.
Glacial striations like these ones were key to developing our understanding of the ice age. In 1842 Charles Lyell visited Halifax and made special trips to examine the striations. Then in 1846, Louis Aggasiz also visited Halifax to examine the marks. These two famous geologists debated the significance of the glacial features. But it was Rev. David Honeyman, the first curator of the Nova Scotia Museum – who first identified the significance of the striations and associated drumlins in 1873 to 1883, to confirm these features were caused by glaciers, massive sheets of ice that covered North America thousands of years ago.