Laccolith vs. Lopolith — What's the Difference?
By Maham Liaqat & Fiza Rafique — Updated on April 28, 2024
A laccolith is a dome-shaped intrusion formed beneath the Earth's surface, bulging upwards, while a lopolith is a large, lens-shaped intrusion that sags downwards.
Difference Between Laccolith and Lopolith
Table of Contents
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Key Differences
A laccolith is characterized by its dome-like shape, typically forming when magma intrudes between rock layers and pushes the overlying strata upward, creating a bulge. In contrast, a lopolith, also resulting from magma intrusion, is distinguished by its concave-upward or lens-like shape, which often leads to the downward sagging of the overlaying strata.
The formation of a laccolith involves less voluminous and more viscous magma, which prevents it from spreading far horizontally, resulting in the uplift and inflation of the rock layers above. On the other hand, a lopolith generally involves more fluid magma that spreads outwards between layers, exerting downward pressure and creating a bowl-like depression.
Laccoliths are typically smaller in scale and affect localized areas within the Earth's crust. This results in isolated, dome-shaped hills or mountains. Lopoliths, however, are often larger and can influence broader geological structures, contributing to significant topographical depressions.
The erosional exposure of a laccolith can reveal spectacular radial patterns and steeply dipping flanks, often visible in mountainous regions. Lopoliths, when eroded, may expose large, synclinal structures that can dominate the landscape with their unique geological formations.
Geologically, laccoliths are important for understanding shallow magmatic processes and are often associated with smaller-scale volcanic activities. Lopoliths provide insights into the dynamics of large-scale magmatic intrusions and their impacts on the structural deformation of the Earth's crust.
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Comparison Chart
Shape
Dome-shaped, bulges upwards
Lens-shaped, sags downwards
Size
Generally smaller
Usually larger
Magma Characteristics
More viscous, less volume
More fluid, larger volume
Geological Impact
Causes uplift of overlying strata
Causes sagging of overlying strata
Visibility
Radial patterns and steep flanks when eroded
Large synclinal structures when eroded
Compare with Definitions
Laccolith
An intrusive body that leads to the formation of isolated mountainous features.
The mining company explored the area around the laccolith for valuable minerals.
Lopolith
A lens-shaped geological structure formed by the spreading of fluid magma.
The lopolith’s lens shape was determined through detailed geophysical surveys.
Laccolith
A type of magmatic intrusion that results in the upward bulging of overlying rock layers.
The laccolith created a prominent hill in the landscape.
Lopolith
A magmatic intrusion that results in the downward sagging of rock layers.
The lopolith under the valley was massive, influencing the area’s geography.
Laccolith
A geological formation involving magma that solidifies before reaching the surface.
Geologists studied the ancient laccolith to understand its magmatic source.
Lopolith
Associated with significant topographical depressions due to its structure.
The depression in the landscape was a direct result of the underlying lopolith.
Laccolith
A shallow intrusion that does not breach the Earth's surface.
The laccolith remained intact despite the erosional forces over millennia.
Lopolith
Often eroded to reveal unique geological patterns.
The eroded lopolith exposed fascinating synclinal structures.
Laccolith
A dome-shaped feature typically found in volcanic regions.
The laccolith’s dome shape was clearly visible from the air.
Lopolith
Typically larger and affects broader geological features.
The lopolith contributed to the formation of the basin in the region.
Laccolith
A laccolith is a sheet-like intrusion (or concordant pluton) that has been injected within or between layers of sedimentary rock (when the host rock is volcanic, the laccolith is referred to as a cryptodome). The pressure of the magma is high enough that the overlying strata are forced upward and folded, giving the laccolith a dome or mushroom-like form (or possibly conical or wedge-shape) with a generally planar base.
Lopolith
A lopolith is a large igneous intrusion which is lenticular in shape with a depressed central region. Lopoliths are generally concordant with the intruded strata with dike or funnel-shaped feeder bodies below the body.
Laccolith
A mass of igneous rock intruded between layers of sedimentary rock, resulting in uplift.
Lopolith
A large, bowl-shaped body of igneous rock intruded between layers of sedimentary rock.
Laccolith
(geology) A mass of igneous or volcanic rock found within strata which forces the overlaying strata upwards and forms domes.
Lopolith
(geology) a mass of volcanic or igneous rock found within strata which has spilled downward into underlaying strata and forms depressed regions.
Laccolith
A mass similar to lopolith but concave up.
Lopolith
(geology) mass similar to laccolith but concave down
Common Curiosities
How does the viscosity of magma affect the formation of a lopolith?
Lopoliths form from more fluid magma, which spreads horizontally between rock layers, causing them to sag due to the weight and spread of the magma.
What landscape features are associated with lopoliths?
Lopoliths are typically associated with basin-like depressions or broad valleys as a result of the sagging strata.
What type of magma is typically involved in forming a laccolith?
Laccoliths are usually formed from more viscous magma that allows the intrusion to bulge upwards without spreading far.
Can a laccolith lead to volcanic activity?
While a laccolith itself is not a volcanic vent, it represents shallow intrusion of magma that could be associated with volcanic activity in the region.
Are laccoliths visible on the earth's surface?
Laccoliths may not be directly visible if buried deep but can form noticeable hills or mountains when the overlying material is eroded away.
What are the research implications of studying laccoliths?
Researching laccoliths can provide insights into crustal deformation processes, magma dynamics, and the thermal history of an area.
What are the environmental impacts of a lopolith?
A lopolith can impact the environment by altering the natural drainage system, influencing sediment deposition patterns, and changing the local landscape.
What is the typical size comparison between a laccolith and a lopolith?
Lopoliths are generally larger than laccoliths, affecting a broader area due to their extensive spread of magma.
How does erosion affect the visibility of a lopolith compared to a laccolith?
Erosion can expose both lopoliths and laccoliths by removing overlying materials; however, laccoliths, with their steep flanks, might become more dramatically exposed.
How do geologists identify a lopolith?
Geologists can identify a lopolith through geological mapping, geophysical surveys, and sometimes through distinctive synclinal formations exposed by erosion.
How does the formation of a laccolith affect the local geology?
The formation of a laccolith can lead to the uplift of geological layers, creating new topography such as hills and potentially influencing local drainage patterns.
What tools do scientists use to study laccoliths?
Scientists study laccoliths using tools like satellite imagery, geological surveys, and rock sampling to understand their composition and structure.
Why are lopoliths less common than other intrusive forms?
Lopoliths require specific conditions such as the availability of large volumes of fluid magma and suitable subsurface structures to support their formation, making them less common.
What is the age range of most laccoliths and lopoliths?
Laccoliths and lopoliths can range from hundreds to millions of years old, depending on their geological context and the timing of the magmatic activity.
Can mining activities be affected by the presence of a lopolith or laccolith?
Yes, the presence of a lopolith or laccolith can affect mining due to the altered rock mechanics and mineral deposits associated with these intrusions.
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Written by
Maham Liaqat
Co-written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
