13.2 Tectonic geomorphology and active faulting
4 min read•july 30, 2024
explores how Earth's surface changes due to tectonic forces and erosion. It's crucial for understanding , revealing how mountains form, rivers change course, and landforms develop over time.
plays a key role in shaping topography. , , and unique are telltale signs of tectonic activity. These features help geologists piece together Earth's dynamic history and predict future changes.
Tectonic Geomorphology: Landscape Evolution
Defining Tectonic Geomorphology
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- Tectonic geomorphology studies interaction between tectonic and surface processes shaping Earth's landscape over time
- Integrates concepts from structural geology, geophysics, and geomorphology to understand tectonic influence on landform development
- Provides insights into rates and patterns of , crucial for assessing and long-term landscape evolution
- Allows reconstruction of past tectonic events and prediction of future landscape changes by analyzing geomorphic features and their relationships
- Essential for understanding dynamic nature of Earth's surface and its response to endogenic and exogenic processes
- Employs various techniques to quantify landscape evolution
- Remote sensing
- Field observations
- Geochronology
- Numerical modeling
Significance in Landscape Evolution
- Reveals interaction between internal and external Earth processes
- Helps identify areas of active tectonism and potential seismic hazards
- Enables reconstruction of past tectonic events ( of )
- Aids in understanding long-term landscape development and erosion patterns
- Provides insights into and deposition in tectonically active regions
- Supports by revealing structural controls on mineral deposits
- Informs land-use planning and infrastructure development in tectonically active areas
Active Faulting Indicators
Topographic Features
- Fault scarps form steep, linear breaks in topography from vertical displacement along fault plane
- Indicate recent or ongoing tectonic activity
- Height and morphology can reveal
- develop as triangular-shaped hillslopes at mountain front bases due to normal faulting and erosion
- Size and steepness relate to fault activity and erosion rates
- create elongated hills from lateral movement of
- Can block or deflect drainage patterns (Carrizo Plain, California)
- and form along strike-slip faults due to local geometry variations
- Pressure ridges: compressional features (uplifted areas)
- Sag ponds: extensional features (depressions often filled with water)
Drainage System Indicators
- Offset streams exhibit abrupt changes in course or channel morphology crossing active fault lines
- Often show lateral displacement (Wallace Creek, San Andreas Fault)
- Tectonic uplift creates in river profiles
- Abrupt changes in channel gradient propagate upstream over time
- and aligned drainage patterns indicate active faults
- Erosion exploits zones of structural weakness
- and develop where rivers cut through uplifting terrain
- Wind gaps: abandoned river courses
- Water gaps: active river courses through uplifted areas
Active Faulting: Shaping Topography
Regional Landform Development
- Active faulting creates and maintains relief in landscapes
- Offsets rock units
- Creates zones of weakness for preferential erosion
- Fault systems control development of major landforms
- Mountain ranges (Sierra Nevada)
- Basins ()
- Valleys ( like East African Rift)
- Interaction between fault-driven uplift and erosional processes determines mountainous terrain morphology
- Fault activity leads to through subsidence
- Affects sedimentation patterns and landscape evolution (San Joaquin Valley, California)
Drainage Network Influence
- Active faulting influences drainage patterns and river network development
- Creates topographic barriers
- Changes base levels
- Alters channel gradients
- Faults can cause or diversion (Gunnison River capture, Colorado)
- Creates localized zones of high erosion rates
- Leads to development of unique geomorphic features (wind gaps, water gaps)
- Influences sediment transport and deposition patterns in fault-bounded basins
- Can cause drainage reversals or formation of in tectonically active regions
Fault Type, Slip Rate, and Landforms
Fault Types and Associated Landforms
- create asymmetric mountain ranges with steep fault scarps and tilted fault blocks
- Example: Wasatch Range, Utah
- produce more symmetrical mountain ranges with thrust-related folding
- Example: San Gabriel Mountains, California
- Strike-slip faults generate characteristic features
- Offset drainages
- Shutter ridges
- (Dead Sea Basin)
- Degree of offset related to fault's and age
Slip Rate and Landscape Evolution
- Slip rates on active faults control rate of landscape change
- Higher slip rates generally produce more pronounced and rapidly evolving geomorphic features
- Interplay between fault slip rate and determines dominant landscape evolution process
- Tectonic uplift vs. surface erosion
- Variations in slip rate along a fault lead to or subsidence
- Creates complex topographic patterns
- Influences drainage network development
- Persistence and preservation of fault-related landforms depend on balance between tectonic activity and surface processes
- Slip rate vs. erosion and deposition rates
- Fault slip rates can be estimated using offset geomorphic markers and dating techniques
- Allows quantification of long-term landscape evolution rates
Key Terms to Review (33)
Active faulting: Active faulting refers to the geological processes associated with faults that have experienced recent movement and are likely to do so again in the future. These faults can cause earthquakes and significantly shape the landscape, impacting everything from landforms to human activities. Understanding active faulting is crucial for assessing seismic hazards and informing land-use planning.
Basin and Range Province: The Basin and Range Province is a geomorphic region in the western United States characterized by a series of elongated mountain ranges separated by down-dropped valleys, known as basins. This province reflects tectonic forces that stretch the Earth's crust, leading to the creation of normal faults and resulting in a distinctive landscape of alternating highlands and lowlands.
Crustal deformation: Crustal deformation refers to the changes in the Earth's crust due to tectonic forces that cause the rocks to deform, resulting in various geological structures like faults, folds, and mountain ranges. This process is essential for understanding how the landscape evolves over time and is closely linked to tectonic geomorphology and active faulting. As tectonic plates move, they exert stress on the crust, which can lead to significant topographical changes and geological hazards.
Differential uplift: Differential uplift refers to the uneven rising of the Earth's surface caused by various geological processes, which can occur over different time scales and spatial extents. This phenomenon is influenced by tectonic forces, volcanic activity, and erosion, leading to the formation of distinct landforms and influencing landscape evolution. Understanding differential uplift is crucial for interpreting active faulting and tectonic geomorphology, as it helps explain how varying rates of uplift can shape the physical features of the Earth’s surface.
Drainage patterns: Drainage patterns refer to the arrangement of streams, rivers, and lakes in a particular area, which reflects the underlying geological and topographical features. They are shaped by various factors including soil type, vegetation, climate, and importantly, tectonic activity that can influence the landscape and water flow. Understanding these patterns helps in interpreting the geological history of an area and the processes that have shaped it over time.
Endorheic basins: Endorheic basins are closed drainage basins that do not allow water to flow out to the ocean or other external water bodies. Instead, water that enters these basins either evaporates or infiltrates the ground, leading to unique hydrological and sedimentary processes. The formation and characteristics of endorheic basins are closely linked to tectonic activity and faulting, as these geological forces can create depressions that trap water and shape the landscape.
Erosion rate: Erosion rate refers to the speed at which soil and rock material is removed from the Earth's surface by natural processes such as water, wind, and ice. Understanding erosion rates is crucial in assessing landscape changes over time, as they reflect the balance between geological uplift and the forces that wear away surfaces. The significance of erosion rates is especially evident when considering how quickly landscapes can change in response to tectonic activities and climatic conditions.
Fault scarps: Fault scarps are steep, often linear landforms that form at the Earth's surface as a result of vertical displacement along a fault line. They are significant indicators of tectonic activity and play a crucial role in understanding how the Earth's crust deforms and changes due to tectonic forces, reflecting the processes involved in active faulting and geomorphology.
Fault slip history: Fault slip history refers to the record of displacement along a fault over time, capturing the frequency, magnitude, and nature of slip events. Understanding this history is crucial for interpreting past seismic activity and assessing future earthquake hazards. By studying fault slip history, researchers can uncover patterns that reveal how faults behave under stress and how they might respond in the future.
Knickpoints: Knickpoints are abrupt changes in the slope of a river or stream channel, often marking the transition between different types of geomorphological features. These features can indicate variations in rock resistance, tectonic activity, or other geological processes that influence river evolution. Knickpoints can be significant for understanding fluvial erosion processes and also provide insights into tectonic geomorphology as they may correlate with active faulting.
Landscape evolution: Landscape evolution refers to the continuous process of change and transformation of the Earth's surface, driven by various physical, chemical, and biological processes over time. It encompasses the interaction between tectonic forces, climate, and erosion, which work together to shape landforms and landscapes, creating features such as mountains, valleys, and plateaus. Understanding this term highlights the dynamic nature of Earth's surface as it responds to environmental changes and geological events.
Linear valleys: Linear valleys are elongated low-lying areas that often form as a result of tectonic activity, erosion, or faulting, and can be significant indicators of geological processes at work. These valleys typically align with geological structures, such as faults or folds, reflecting the influence of tectonic forces over time. Their formation can be linked to active faulting, where movement along a fault line creates a distinct valley shape.
Mountain ranges: Mountain ranges are large, linear groups of mountains that are typically formed through tectonic processes such as the collision of tectonic plates, volcanic activity, or erosion over time. These geological features are significant because they influence climate, ecosystems, and human activities, often serving as natural barriers and affecting weather patterns.
Natural Resource Exploration: Natural resource exploration refers to the systematic search for and evaluation of resources such as minerals, oil, gas, and water found within the Earth's crust. This process involves various methods, including geological surveys, geophysical techniques, and drilling operations, to identify and assess the quality and quantity of these resources. It is closely tied to understanding the geological settings and processes that shape the Earth’s surface, particularly in areas with tectonic activity and active faulting.
Normal faults: Normal faults are geological fractures where the hanging wall moves downward relative to the footwall due to extensional forces acting on the Earth's crust. This movement often occurs in areas experiencing tectonic divergence, leading to the formation of rift valleys and other distinctive landforms that showcase the effects of active faulting and tectonic geomorphology.
Offset streams: Offset streams are river channels that have been displaced laterally due to tectonic activity, particularly along fault lines. These streams exhibit a characteristic shift in their course, often creating a noticeable separation between the original stream path and the current flow. This phenomenon provides key insights into tectonic geomorphology and helps in understanding active faulting processes.
Pressure Ridges: Pressure ridges are prominent landforms created by the compression of tectonic plates, leading to the upward movement of rock layers. These features are commonly found in areas of active faulting and tectonic activity, illustrating the dynamic nature of Earth's surface and providing insight into the forces at play in the lithosphere.
Pull-apart basins: Pull-apart basins are geological depressions formed by the extension and lateral movement of tectonic plates, typically occurring in regions where faults intersect or diverge. These basins are a result of the tectonic forces that stretch the Earth's crust, causing it to fracture and create areas of subsidence. This process often leads to the development of features like sedimentary deposits and various landforms associated with faulting and rifting.
Reverse faults: Reverse faults are a type of fault where the hanging wall moves upward relative to the footwall due to compressional forces. This movement occurs when tectonic plates push against each other, leading to the shortening of the Earth's crust. Reverse faults are significant in understanding tectonic geomorphology and active faulting as they play a critical role in mountain building and seismic activity.
Rift valleys: Rift valleys are elongated depressions that form when tectonic plates move apart, leading to the subsidence of the land between them. These valleys are significant geological features that result from tectonic activity, often associated with divergent boundaries where the Earth's lithosphere is being pulled apart, leading to volcanic activity and unique ecosystems.
River capture: River capture is a geomorphological process where one river system erodes and diverts the flow of another river, effectively capturing its drainage basin. This phenomenon often results from tectonic activity or changes in the landscape that affect the flow patterns of rivers, making it an important concept in understanding how landforms evolve over time.
Sag Ponds: Sag ponds are depressions that form in the landscape due to the movement of tectonic plates, specifically in areas where faults create a down-dropped block of land, known as a graben. These ponds typically accumulate water, leading to their characteristic appearance and providing unique ecological niches. Sag ponds are important for understanding geological processes, as they serve as indicators of active faulting and can reveal information about the tectonic history of an area.
Sediment transport: Sediment transport refers to the movement of solid particles, typically resulting from processes such as erosion, weathering, and deposition, through various environmental mediums like water, wind, or ice. This process is crucial for shaping landscapes and influencing ecological systems, as it plays a key role in sediment delivery to river channels, coastal areas, and other depositional environments.
Sedimentary basin formation: Sedimentary basin formation refers to the processes that create depressions in the Earth's crust where sediments accumulate over time. These basins often form due to tectonic activity, such as rifting or subsidence, which creates low-lying areas that can trap sediments brought by rivers, wind, or glaciers. The characteristics of these basins play a crucial role in understanding sedimentary processes, the geological history of an area, and the potential for natural resources like oil and gas.
Seismic hazards: Seismic hazards refer to the potential risks and dangers associated with earthquakes and the effects they can have on the built environment and natural landscapes. These hazards include ground shaking, surface rupture, liquefaction, landslides, and tsunamis, which can all result from tectonic movements. Understanding seismic hazards is essential for assessing the impact of active faulting on communities and infrastructure in areas prone to earthquakes.
Shutter Ridges: Shutter ridges are topographic features formed as a result of horizontal displacement along faults, where they act as barriers that create a distinct offset in the landscape. These ridges are formed by the uplift and erosion of faulted rock, creating a visible marker of tectonic activity and a record of fault movement. The presence of shutter ridges can indicate the direction and magnitude of past tectonic forces, helping geologists understand the dynamics of active faulting.
Slip Rate: Slip rate is the measure of the relative motion between two tectonic plates along a fault, expressed as the distance of displacement per unit of time, typically in millimeters per year. This term is crucial for understanding how active faults behave and evolve over time, as it helps estimate the rate at which stress builds up and is released during earthquakes. It also plays a significant role in assessing earthquake hazards and understanding landscape changes driven by tectonic activity.
Strike-slip faults: Strike-slip faults are geological fractures where two blocks of crust slide past each other horizontally due to shear stress. These faults are characterized by lateral movement, which can result in noticeable displacements along the fault line, often leading to distinct landforms and features in tectonic geomorphology. The movement occurs parallel to the fault plane, which means that the ground on either side of the fault can shift laterally without significant vertical displacement.
Tectonic geomorphology: Tectonic geomorphology is the study of the relationship between tectonic processes and the Earth's surface landforms. It focuses on how geological forces, such as faulting, folding, and volcanic activity, shape landscapes over time. This branch of geomorphology investigates how these processes create various landforms and influence erosion, sedimentation, and topography.
Triangular facets: Triangular facets are geomorphic features that appear as triangular-shaped landforms often found on fault scarps or along the edges of uplifted blocks in tectonically active regions. These facets are indicative of erosional processes acting on newly exposed rock surfaces and reflect the dynamic interplay between tectonic uplift and weathering. They often serve as a visual marker of tectonic activity, helping to identify past fault movements and landscape evolution.
Uplift history: Uplift history refers to the chronological record of the vertical movements of Earth's crust that lead to the elevation of land surfaces, often influenced by tectonic forces. This concept is essential in understanding how landscape features evolve over time, as well as their current forms and distributions. Recognizing uplift history can help scientists decipher the interactions between tectonic activity and surface processes, revealing insights into landform development and active faulting.
Water Gaps: Water gaps are river valleys that have been eroded through ridges or hills, forming a channel where the river has cut through rock layers. These features are often indicators of the geological history and tectonic activity of an area, providing insights into how landscapes evolve in response to both erosional processes and tectonic uplift.
Wind gaps: Wind gaps are geographical features that represent the remnants of an ancient river valley where water flow has ceased, often due to tectonic uplift or changes in the landscape. They are typically characterized by a dry streambed or valley that once conveyed water but is now exposed to the wind, providing evidence of past drainage systems that have been altered by geological processes.