Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
Muzzammil Ismail, profile picture
Uploaded byMuzzammil Ismail
PPTX, PDF80 views

Gr 11 - Geography - Granite Doms and Tors - Ismail M.

This presentation explores the formation of granite domes and tors, two distinct landforms that originate from massive underground igneous intrusions like batholiths and laccoliths. Learn how the slow cooling of magma deep below the surface creates these features, and how millions of years of erosion expose them. Discover the role of exfoliation weathering in shaping smooth, rounded granite domes (such as Paarl Dome), and contrast this with the jagged, blocky tors formed by chemical weathering along joint planes underground. The slides include a critical exam fact about the balance between surface erosion and chemical weathering, as well as a thought-provoking discussion question on why past climates were more influential in forming these landscapes than today’s climate. Perfect for Grade 11 Geography revision.

Education◦
Download to read offline
Topography Associated with Massive Igneous Rocks Characteristics and Processes of Granite Domes and Tors GRADE 11 – TERM 2 By Mr. Ismail
Lesson Objectives By the end of this lesson, You should be able to: Identify & Describe Identify and describe at least three visual characteristics of a granite dome (bornhardt). Explain Formation Explain the step-by-step sequence of tor formation, from deep-seated jointing to final surface exposure. Compare & Contrast Compare a granite dome with a tors landscape, justifying which geomorphic process (exfoliation vs block disintegration) dominates each landform. 2 1 3 Kahoot Quiz Link: https://create.kahoot.it/share/gr-11-geography-granite-doms-and-tors/64250692-a6cc-4e2c-bbb4-41732197eab6
How It All Starts: Deep Underground The Origin Story — Batholiths & Laccoliths  Granite domes and tors originate from batholiths and laccoliths, which are massive bodies of igneous rock that formed deep below the Earth's surface when molten magma cooled and solidified over millions of years.  These intrusions are enormous in scale, often underlying entire mountain ranges. Batholith A very large igneous intrusion that cuts across existing rock layers. Batholiths underlie most granite dome landscapes and can extend hundreds of kilometers. Laccolith A dome-shaped igneous intrusion that forces overlying strata upward. Smaller than a batholith, it causes the surface rock layers above it to arch and bulge upward.
From Underground to Surface Exposure and Erosion — The Big Reveal  As the overlying layers of rock were gradually eroded over millions of years, the granite mass beneath was slowly exposed at the surface.  This long-term stripping process is what creates the dramatic landforms we see today. Batholith Forms Granite crystallizes deep beneath strata Layers Erode Overlying rock is worn away gradually Granite Exposed Batholith emerges as a surface dome Key Term — Granite Dome: A landform resulting from the erosion of overlying strata to expose a batholith at the Earth's surface. The exposed rock then undergoes further weathering to produce its characteristic rounded shape.
Identifying a Granite Dome Shape Large, dome-shaped landform (also called a Bornhardt) with a smooth, rounded, convex appearance rising prominently above the surrounding landscape. Texture Smooth, curved surface with sheets of rock that have peeled away through exfoliation weathering, leaving a polished, onion-like outer layer. Origin Results directly from the exposure of a batholith after millions of years of overlying rock erosion. The batholith itself was formed from slowly cooled magma. 1st Uluru, Australia World's largest granite dome (Ayers Rock) 2nd Sibebe Rock Second largest granite dome — located in Swaziland SA Paarl Rock South African example — situated near Cape Town Link to YouTube Video on Granite Domes and Tors: https://youtu.be/2q1_-dhFCQs?si=MqOnSNYsqQukm
How Do Domes Get Their Shape? The Shaping Process — Exfoliation Weathering  The smooth, rounded shape of a granite dome is produced by a process called exfoliation (also known as sheeting).  This occurs due to pressure release joints that develop as overlying rock is removed — the granite expands upward and outward, and curved cracks form parallel to the surface.  Exfoliation weathering is further driven by thermal expansion and contraction: the outer rock layer heats and expands during the day, then cools and contracts at night.  Over time, this repeated stress causes sheets of rock to peel off the dome — much like the layers of an onion. Vocabulary — Exfoliation: The peeling off of curved rock sheets from a granite surface due to pressure release and repeated heating and cooling cycles. Mechanism Summary  Overlying rock is removed → pressure decreases  Granite expands → pressure release joints form  Daily heating rock → expands  Nightly cooling rock → contracts  Repeated stress → sheets peel off
What About Those Stacks of Boulders? Introduction to Tors — A Different Landscape Tor — Carbilly Tor/Arthurs Sword, Cornwall (England)  A tor is an exposed mass of granite made up of large, angular, blocky boulders stacked upon one another.  The surface is rough, jagged, and irregular — the complete opposite of a smooth dome. Granite Dome — Paarl Dome (Western Cape)  A granite dome has a smooth, rounded, convex surface shaped by exfoliation.  There are no loose blocks — the surface is a continuous, gently curved sheet of rock. Key Definition — Tor Exposed granite blocks made up of core stones rounded granite boulders left behind after the surrounding, more jointed rock has been chemically weathered and eroded away. Key Definition — Core Stones Granite boulders that remain after the surrounding rock has been weathered. They form underground along widely spaced joints where chemical weathering is less intense, leaving rounded resistant blocks in a matrix of weathered debris (grus).
The Secret Life of Tors Tor Formation: The Underground Phase Tors are caused by the chemical weathering of granite along joints — natural cracks in the rock — deep below the Earth's surface. Groundwater seeps along these joints and chemically weathers the rock, rounding the edges of each block over a very long period of time. Widely Spaced Joints TORS FORM →  When joints are far apart, large blocks of rock remain relatively unweathered between the joints.  These blocks survive as core stones surrounded by weathered debris (grus).  After erosion, these core stones are exposed as a tor. Closely Spaced Joints NO TORS FORM →  When joints are close together, chemical weathering penetrates the entire rock mass.  The granite is completely broken down into fine, weathered debris (grus).  No resistant blocks survive, and therefore no tors can form. Remember: • The spacing of joints is the single most critical factor in determining whether a tor will form. • Widely spaced joints = large surviving core stones = potential tor landscape.
The Secret Life of Tors Tor Formation: The Underground Phase
From Hidden Blocks to Visible Landmarks Tor Formation — The Exposure Phase 🇿🇦 South Africa Tors are found in the northern part of the Northern Cape province. For a tor to appear at the surface, a critical condition must be met: the rate of erosion of the Earth's surface must be greater than the rate of chemical weathering of the granite below. This ensures that the loose weathered debris (grus) is stripped away before the core stones are themselves weathered. Deep chemical weathering along joints forms core stones surrounded by grus (soft, weathered debris) underground. Surface erosion strips away the loose weathered material (grus) faster than new weathering occurs underground. Core stones are left standing on the bedrock as exposed, stacked granite boulders — a tor landscape. Stage 1 Stage 2 Stage 3
From Hidden Blocks to Visible Landmarks Tor Formation — The Exposure Phase Zimbabwe The Matopos (Matobo Hills) — internationally well-known tor landscape. 🇬🇧 England Dartmoor & Cornwall — classic tors including Carbilly Tor.
Summary: Granite Dome vs Tor Critical Exam Fact: Tors only form if the rate of surface erosion is greater than the rate of underground chemical weathering. If weathering is faster, no core stones survive and no tors form. (Source: Page 144) Conclusion Question for Discussion: Why do geographers argue that past climates were more important in forming these features than today's climate? Consider what conditions would have been needed for the rate of erosion to exceed the rate of chemical weathering over such large areas. Feature Granite Dome (Bornhardt) Tor (Corestone Landscape) Shape & Appearance Large, smooth, rounded convex dome Stack of loose, angular, blocky boulders (corestones) Dominant Process Exfoliation (Peeling / Sheeting) Deep chemical weathering along joints Key Mechanism Thermal expansion and contraction (Physical Weathering) + pressure release Widely spaced joints required; erosion removes regolith to reveal blocks Critical Condition Overlying strata must be completely eroded to expose batholith Rate of surface erosion must exceed rate of underground chemical weathering South African Example Paarl Rock (near Cape Town) Northern parts of the Northern Cape International Example Sibebe Rock (Swaziland); Uluru (Australia) Matopos (Zimbabwe); Dartmoor, (England)
Homework Activity
Homework Activity