Tor Meaning
Tors are typically the exposed rock mass of the jointed and broken blocks. These tors are known as either castle koppie or kopje by geomorphologists. Also, these tors large, free-standing outcrops of rocks that rise abruptly from the surrounding slopes that are smooth and gentle as they are a part of the rounded hill summit or the crest of a ridge. It is also a term that is commonly used in the southwest of England for hills especially the hills and the high points located in Dartmoor in Devon and Bodmin Moor of Cornwall. Tor meaning is from the English language which defines it as a bare mass of rock that is surmounted and surrounded by groups of blocks and boulders which is further derived from the old English word ‘torr’.
How Tors are Formed?
As per the Tor meaning, it is clear that they are exposed forms of rocks. Hence, it is clear that the rots are the landforms which are the landforms created due to the erosion and weathering of the rock that surrounds it. The surrounding rocks are mostly composed of granites but also contain shists, dolerites, dacites and ignimbrites and also coarse sandstones and others. The tor geography depicts its height as less than 5 meters. Many of the hypotheses that are laid down to understand how tors are formed have tried to propose and explain their origin but yet this topic remains a part of discussion amongst geologista, geomorphologists and physical geographers. An agreed-upon hypothesis states that the tor geography was formed by the geomorphic processes that differ widely in type and duration. These differences are said to be the attributes of the regional and local differences that occur in the climate and the different rock types.
An example of tor geography explaining how tors are formed is the Dartmoor granite which was emplaced almost around approximately 300 million years ago. This happened along with the erosion of the cover rocks. Due to this erosion, the Dartmoor granite rock lay exposed to the chemical and physical weathering processes. Wherever the joints are found to be closely spaced, the large crystals present in the granite stone readily disintegrated which resulted in the formation of a sandy regolith which was locally known as growan. This is found to be readily stripped off by using the solifluction process or also by the surface wash when it was not protected by vegetation. This process significantly continued during the prolonged phases of cold climate during the Quaternary Ice ages which are known as periglaciation.
Wherever the joints are found to be unusually widely spaced, the cores blocks are known to survive and escape the above-mentioned weathering processes. As a result, they formed the tors. These tors can be monolithic like the ones at Haytor and Blackingstone Rock or subdivided into stacks as more usually found and often arranged in the form of avenues. Each of the stacks is known to comprise several layers or tiers or pillows, which may have become separated. In this case, the rocking pillows are known as logan stones. Furthermore, these stacks are found to be vulnerable to frost action and are often collapsing which is understood from the trails of blocks present down the slopes known as clitter or clatter. Weathering also gives rise to the circular ‘rock basins’ formed by the accumulation of the water and the repeated freezing and thawing as found in the case of Kes Tor on Dartmoor.
In the region of Dartmoor, when 28 tors were subjected to the process of dating, it showed that most of them are still young. This is determined as most of them are less than 1,00,000 years old and none of them is over 2,00,000 years old. They must have probably emerged at the start of the last major ice age - the Devensian. In contrast to this, the Scottish Cairngorms are other classic granite tor concentrations found in Britain with the oldest tors amongst them being between 200 and 6,75,000 years old and also the glacially modified regions having dates in-between 100 to 1,50,000 years. These tors reflect a more dry and more arctic climate.
An image of the Tor is shown below:
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FAQs on Tors
1. What is a tor in the context of geography?
A tor is a distinctive landform consisting of a large, free-standing rock outcrop that rises abruptly from the gentle slopes of a rounded hill or ridge crest. Often composed of jointed and weathered granite, they are also known by geomorphologists as a 'castle koppie' or 'kopje'. Their appearance can range from a single, massive boulder to a stack of weathered blocks.
2. How are tors formed through geological processes?
Tors are typically formed through a two-stage process. The first stage involves subsurface chemical weathering, where groundwater penetrates joints (cracks) in the bedrock, like granite, decomposing the rock into a mass of weathered material called regolith. In the second stage, this surrounding loose material is stripped away by erosion (by wind, water, or ice) and mass wasting, exposing the more resistant, unweathered corestones as an exposed tor.
3. What is the main difference between a tor and a hill?
The main difference lies in their scale and composition. A hill is a general term for an elevated landform made of rock and soil, smaller than a mountain. In contrast, a tor is a specific rock feature—an exposed outcrop of bedrock—that is typically found on the summit or slopes of a hill. Therefore, a tor can be a feature on a hill, but a hill is not a feature on a tor.
4. Why are tors predominantly found in granitic landscapes?
Tors are most commonly associated with granite because of its specific properties. Granite is a hard, crystalline igneous rock that is highly resistant to erosion, but it is also characterised by a network of vertical and horizontal cracks called joints. These joints are crucial as they allow water to seep deep into the rock mass, initiating the weathering processes that are essential for breaking down the surrounding rock and eventually forming a tor.
5. What are the two main competing theories that explain the formation of tors?
The two primary scientific theories explaining how tors are formed are:
- The Two-Stage (Subsurface Weathering) Theory: Proposed by David Linton, this widely accepted model suggests tors form from deep chemical weathering below the ground, which rots the rock along joints. This is followed by a period of erosion that strips away the weathered material, exposing the solid corestone.
- The Periglacial Theory: This theory argues that tors are formed in cold, periglacial climates. The primary mechanism is freeze-thaw action, where water freezes and expands in cracks, breaking the rock apart. The resulting debris is then removed by processes like solifluction (slow, downslope movement of saturated soil).
6. What is the importance of studying tors for understanding past climates?
Tors are significant climatic indicators, acting as relics of past environments. Finding a well-developed tor in a region that is currently temperate can provide strong evidence that the area experienced a much colder, periglacial climate during a past Ice Age. They help geographers and geologists reconstruct the landscape history and understand long-term climatic shifts.
7. Are tors natural formations or are they man-made?
Tors are entirely natural geological formations. Despite their often unusual and sculpted appearance, they are the result of millions of years of natural processes, not human activity. The key mechanisms are the differential weathering of rock along its internal joint patterns and the subsequent erosion of the weaker, surrounding material, leaving the resistant core exposed.
8. Where can one see examples of tors in India and around the world?
Tors are found in various granite-rich landscapes globally.
- In India: Notable examples can be found across the Deccan Plateau, especially around Hampi in Karnataka, and in parts of the Aravalli Range in Rajasthan and the Chota Nagpur Plateau.
- Worldwide: Classic examples include the iconic tors of Dartmoor and Bodmin Moor in England. They are also prominent features in the Cairngorms of Scotland, parts of Australia, and Africa.
