🌍 Introduction
Constructed in 1857, MacNab Street Presbyterian Church is a beautiful example of Gothic Revival architecture in Hamilton. The building was constructed using locally sourced stone from the Niagara Escarpment, reflecting both the natural geology of the region and the building practices of the time.
While the architecture is impressive, this EarthCache focuses on the geological story preserved within the stone itself. The building stones record ancient environments from hundreds of millions of years ago and also show how modern urban conditions continue to shape and reveal these features today.
🧭 Geological Focus
This EarthCache explores:
- Cross-bedding in sandstone
- Ancient sedimentary environments
- How pollution reveals internal rock structures
- Differences in weathering between rock types
🪨
The Geology of the Stone
The upper portion of the church is built primarily from Whirlpool Sandstone, a sedimentary rock formed approximately 430 million years ago during the Silurian Period.
🌊 How This Rock Formed
At that time, this area was covered by shallow seas and coastal environments. Sand was moved by waves and currents, forming ripples and underwater dunes.
Over time:
- Sand layers were deposited
- These layers were buried
- Pressure and minerals cemented them into rock
🔍 What is Cross-Bedding?
Cross-bedding is a sedimentary structure formed when moving water or wind creates sloping layers inside the sand.
Instead of flat layers, the sand forms angled layers as dunes migrate.
At this site, cross-bedding appears as:
- Slanted or diagonal lines within the stone
- Repeating angled patterns
- Different directions from block to block
👉 Each block was cut from rock that had a different orientation, which is why the angles vary.
🌫️ Pollution Revealing the Past
In the late 1800s, nearby railway activity produced soot and pollution. This caused black staining on the sandstone.
But something interesting happened:
- The staining followed the internal layers of the rock
- These layers are slightly more porous
- The result is that cross-bedding is now much easier to see
👉 Pollution has helped reveal the hidden structure of the rock.
🧱 Base Stones – A Different Story
Near the base of the building, you will notice stones that look very different:
- Lighter in colour
- More worn or rounded
- Different staining patterns (including rust colours)
These stones are likely limestone or dolostone, which are chemically different from sandstone.
Because of this:
- They weather differently
- They react differently to water and pollution
- They break down in a different way
👉 This gives you a chance to compare how rock type affects weathering.
🔎 Logging Tasks
In order to log this EarthCache, please email me the answers to the following questions using the information that you found on the cache page and at the physical site.
1. Look at the sandstone blocks above the doorway.
Describe the pattern of the dark lines you see.
👉 Are they horizontal, vertical, or angled?
2. Find a block where the lines are very clear.
Describe the direction of the lines (for example: slanted left or right).
3. Explain what these angled lines represent in terms of how the rock originally formed.
4. Look closely at the black staining on the sandstone.
Why does the staining follow lines instead of spreading evenly?
5. Now look at the base stones near ground level.
Describe two differences between the base stones and the sandstone above (colour, texture, or weathering).
6. Why do the base stones weather differently than the sandstone?
7. MANDATORY: Post a picture of you or a personal item at the posted coordinates with the Macnab Street Presbyterian Church in the background from the posted coordinates (north side of the building).
Congratulations to boekmeisje on the FTF!