Crystalline Forms and Volcanic Mass: A Geomorphological Analysis
Crystalline Forms and Volcanic Mass
Crystalline Masses
The term “rock crystal” is useful for referring collectively to intrusive igneous and metamorphic rocks, such as anorthosites and gneiss. They are divided into groups:
Homogeneous Crystalline Masses
These are huge intrusive granite bodies, sometimes kilometers deep, that reach the surface through erosion. Their topographical development varies; the texture and composition of the rock mass depend on whether or not it has been faulted. Once a batholith reaches the surface, it forms a landscape of hills called lomerío, separated by small valleys. Homogeneity exists in both the rock and the relief.
Drainage Patterns
Drainage patterns are composed of dendritic and subsequent watercourses, similar to horizontal sedimentary strata. Where there is no river, failure always occurs. When the rock contains parallel faults, the fault may be reflected in the drainage pattern, resulting in a regular drainage pattern.
Metamorphic Belts
In these regions, the topography reflects the different rates of denudation of parallel zones of metamorphic rocks: shale, slate, quartzite, marble, etc. Marble tends to cause characteristic valleys, while shale and shale mountains rise in aqueous mediums, often forming rough quartzite reliefs that may lead to narrow hogbacks.
- Association of metamorphic rocks that behave differently when attacked by external agents.
Thrust Faults
Thrust faults also correspond to predominantly horizontal motion, but with a flat fault plane where one block rides on the surface of another.
Grabens
A graben occurs when a block drops between two normal faults. Grabens are characteristic of fractured zones of shields. When defining the tectonics, the landscape transforms into a mountain with rolling, regular profiles. Sediments accumulating in the sunken blocks can cause them to sink further due to weight.
Horsts
Horsts are mountains or plateaus that often have a full top and steep slopes, but also a rectilinear profile.
Erosive Development of a Fault Scarp
Young Fault Scarps
The escarpment remains straight, even after some years of erosion by water currents, and its base features fans and alluvial fans.
Fault Scarp in a State of Maturity
Weathering and erosion have caused the decline of the escarpment, making its plan view completely irregular.
- The resistant lip covering the fault has been totally destroyed, and the underlying soft formation has eroded quickly to a level lower than the sunken lip, where resistant bedrock remains intact.
- The region has been reduced to a peneplain, and the escarpment has been completely destroyed. The area on both sides of the fault line has the same height.
- Erosion has created a model after another fault line scarp. Its appearance is due to the erosion of the sedimentary cover that existed on both sides of the fault, exposing the igneous rock basement upon which eroded materials had been deposited.
Jogger Blocks
These are regions where failure to acquire large-scale displacement of hundreds of meters causes mountain masses. A tilted block presents a steep face (the fault scarp) and a gentle slope. The initial watershed is near the top of the fault scarp and is therefore situated on the banks of a block.
Evolution
During the domestic stage of erosion, irregular angular shapes transform into ordinary mountains. The remains are a series of triangular shapes called triangular facets.