13.3 Uplift, subsidence, and their geomorphic effects
3 min read•july 30, 2024
Uplift and shape Earth's surface, creating diverse landscapes. These processes, driven by plate tectonics, alter elevation and relief, influencing erosion rates, river systems, and coastal features. Understanding their effects is crucial for grasping landscape evolution.
Tectonic forces cause vertical movements that interact with erosion, sedimentation, and sea-level changes. This dynamic interplay creates landforms like mountains, valleys, and coastal plains. Isostatic adjustments further complicate the picture, adding another layer to Earth's ever-changing surface.
Tectonic Uplift vs Subsidence
Vertical Displacement and Tectonic Settings
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- vertically displaces Earth's surface upward due to plate tectonic forces, increasing elevation
- Subsidence moves Earth's surface downward, decreasing elevation
- Uplift typically occurs in compressional tectonic settings (convergent plate boundaries)
- Subsidence often happens in extensional settings or sedimentary
- Rate and duration of uplift or subsidence determine resulting landforms and geomorphic processes
Geomorphic Consequences
- Uplift increases relief, steepens slopes, and enhances erosion rates
- Forms deeply incised valleys, gorges, and rejuvenated landscapes
- Subsidence creates sedimentary basins, coastal plains, and submerges land areas
- Develops for sediment accumulation
- Both processes change base level, affecting river systems
- Alters erosional and depositional patterns
- Examples of uplift-induced landforms (Rocky Mountains, Andes)
- Examples of subsidence-induced features (North Sea Basin, Mississippi Delta)
Uplift and Subsidence Impacts on Erosion
Erosion Rates and Sediment Transport
- Uplift increases erosion rates by steepening slopes and increasing stream gradients
- Enhances stream power and sediment transport efficiency
- Subsidence decreases erosion rates in subsiding areas
- Increases erosion in adjacent uplifted regions
- Creates accommodation space for sediment deposition
- Interaction between uplift/subsidence rates and erosion rates determines landscape equilibrium state
- vs. disequilibrium
- Alters sediment transport patterns from source to sink
- Affects sediment distribution across landscapes
River Systems and Drainage Patterns
- Uplift causes river incision and terrace formation
- Subsidence leads to river aggradation and alluvial plain development
- Base level changes shift erosional and depositional zones within drainage basins
- Influences drainage pattern development
- Antecedent streams (Colorado River through Grand Canyon)
- Drainage reversals (Amazon River)
- Examples of uplift-induced river changes (Yangtze River gorges)
- Examples of subsidence-induced river changes (Mississippi River delta)
Coastal Landscapes: Uplift vs Subsidence
Coastal Landform Development
- Coastal uplift forms marine terraces
- Flat, elevated surfaces representing former sea levels
- Record past sea-level changes and tectonic activity
- Uplift causes emergence of wave-cut platforms and sea cliff formation
- Subsidence develops extensive coastal plains
- Submerges former land surfaces
- Creates estuaries and drowned river valleys
- Subsidence leads to drowning of coastal features and barrier island development
- Interplay between uplift/subsidence rates and sea-level changes determines coastline transgression or regression
- Examples of uplifted coasts (California coast)
- Examples of subsiding coasts (Louisiana Gulf Coast)
Preservation and Abrupt Changes
- Uplift/subsidence rate relative to sea-level change influences coastal landform preservation
- Tectonic activity causes abrupt coastal landscape changes
- events create new land
- Sudden subsidence submerges coastal areas
- Impact varies based on rock type, sediment supply, and wave energy
- Examples of preserved uplifted coastlines (Napier, New Zealand)
- Examples of rapidly subsiding coastlines (Venice, Italy)
Isostatic Adjustments in Response to Tectonics
Isostatic Principles and Tectonic Influences
- Isostasy maintains gravitational equilibrium between Earth's crust and mantle
- Crust "floats" on denser mantle
- Isostatic adjustments occur to maintain equilibrium when crustal loading or unloading changes
- Tectonic processes cause isostatic adjustments as crust thickens or thins
- Mountain building or rifting leads to vertical surface movements
- Adjustment rate depends on mantle viscosity and load change magnitude
- Results in delayed landscape responses to tectonic or erosional events
Erosional and Glacial Isostatic Adjustments
- of mountain ranges triggers isostatic uplift ()
- Prolongs mountain range lifespan
- Influences geomorphic evolution
- responds to ice sheet loading and unloading
- Causes vertical surface movements continuing long after ice melts
- Isostatic adjustments influence regional drainage patterns and sediment transport pathways
- Redistributes erosional and depositional zones
- Examples of erosional isostatic rebound (Appalachian Mountains)
- Examples of glacial isostatic adjustment (Scandinavia)
Key Terms to Review (21)
Accommodation space: Accommodation space refers to the volume of space available for sediment to accumulate in a geological setting. It is influenced by various geological processes, such as uplift and subsidence, which either create or reduce the available space for sedimentation. Understanding accommodation space is crucial for interpreting sedimentary environments and the resultant stratigraphy.
Basins: Basins are low-lying areas on the Earth's surface where water collects, either from precipitation, runoff, or groundwater flow. These geological formations can take various forms, including river basins, lake basins, and sedimentary basins, which are shaped by processes like uplift and subsidence, influencing the surrounding landscape and ecosystems.
Coseismic uplift: Coseismic uplift refers to the immediate vertical rise of the Earth's surface that occurs during an earthquake as a result of the sudden release of stress along geological faults. This phenomenon can lead to significant changes in the landscape, contributing to the formation of new topographic features and altering existing ones. Understanding coseismic uplift is crucial for comprehending how earthquakes affect landforms and influence geomorphic processes in the surrounding areas.
Differential erosion: Differential erosion refers to the process where different materials or landscapes erode at varying rates due to factors like composition, hardness, and environmental conditions. This phenomenon results in varied landforms and topographies, shaping the Earth’s surface in unique ways. Understanding differential erosion is crucial in recognizing how fluvial systems interact with geological structures and how uplift or subsidence can create distinct geomorphic features.
Dynamic Equilibrium: Dynamic equilibrium refers to a state of balance in which processes are constantly changing, but the overall system remains stable over time. In the context of Earth surface processes, this concept illustrates how landforms evolve due to various factors like erosion and deposition while still maintaining a certain degree of balance in their characteristics. Understanding this equilibrium helps in comprehending how landscapes respond to changes in environmental conditions, whether they be natural or anthropogenic.
Earthquakes: Earthquakes are sudden shaking or trembling of the ground caused by the movement of tectonic plates along faults. This geological phenomenon is a direct result of the release of energy accumulated due to stress in the Earth's crust, which can lead to significant changes in the landscape and affect geological processes such as uplift and subsidence.
Erosional Unloading: Erosional unloading is the geological process where overlying material, such as rock and soil, is removed or eroded away, leading to a reduction in pressure on the underlying layers. This process can result in the uplift of those layers due to isostatic rebound, where the Earth's crust adjusts to the removal of weight. It plays a critical role in shaping landscapes, influencing both landform development and geological processes.
Fault-block mountains: Fault-block mountains are large mountain ranges formed from blocks of the Earth's crust that have been lifted or tilted due to tectonic forces, particularly faulting. These mountains typically appear jagged and steep, as the blocks of rock are created when tectonic plates move apart or collide, causing sections of the Earth's crust to fracture and shift. Their formation is closely tied to processes like uplift and subsidence, which contribute to the shaping of the landscape.
Geomorphic equilibrium: Geomorphic equilibrium refers to a state where the landforms in a particular area are stable and in balance with the processes that shape them, such as erosion and sediment deposition. In this state, the forces acting on the landscape, like uplift and subsidence, are countered by processes that redistribute materials, maintaining a consistent form over time. This dynamic balance is crucial for understanding how landscapes evolve in response to both natural processes and human activities.
Glacial Isostatic Adjustment: Glacial isostatic adjustment is the process by which the Earth's crust rebounds after being compressed by the weight of ice sheets and glaciers during glacial periods. This rebound occurs as the ice melts, leading to the gradual uplift of land that had previously been depressed. The ongoing adjustments have significant implications for sea levels, landscape evolution, and even the distribution of ecosystems in affected areas.
GPS Monitoring: GPS monitoring refers to the use of Global Positioning System technology to track and record the precise location of objects or land over time. This technology allows for real-time data collection, which is crucial in understanding and assessing the movement and stability of landscapes, particularly in relation to hazards such as landslides and geological uplift or subsidence. By providing accurate spatial information, GPS monitoring enhances risk assessment efforts and helps predict potential geological changes that can impact the environment and human safety.
Habitat alteration: Habitat alteration refers to the changes made to natural environments, often due to human activities, which can significantly impact the living conditions for various species. This concept encompasses alterations in physical landscape, vegetation, and hydrology that may lead to fragmentation or degradation of ecosystems. The effects of habitat alteration can influence biodiversity, species interactions, and the overall health of ecological systems.
Isostatic Rebound: Isostatic rebound refers to the process where the Earth's crust rises after being compressed by the weight of ice sheets or other heavy loads. This adjustment occurs after the melting of ice or the removal of weight, allowing the crust to gradually regain its equilibrium. This phenomenon is crucial in understanding landscape changes and geological processes following glaciations, erosion, and shifts in sea levels.
John Hack: John Hack refers to a significant figure in the study of geomorphology, particularly known for his contributions to understanding uplift and subsidence processes and their impact on landscape evolution. His work emphasizes the importance of tectonic forces in shaping landforms and examines how changes in elevation influence erosion, sedimentation, and landform development over time.
Satellite remote sensing: Satellite remote sensing is the acquisition of information about Earth's surface using satellite technology to observe and analyze spatial data from a distance. This technique enables scientists and researchers to monitor changes in the environment, such as uplift and subsidence, and their associated geomorphic effects, helping to understand processes like landform evolution and landscape dynamics over time.
Soil development: Soil development refers to the processes through which soil forms and evolves over time, influenced by factors such as parent material, climate, organisms, topography, and time. This term highlights the dynamic nature of soils as they undergo physical, chemical, and biological changes that contribute to their formation. The interplay of these factors can lead to varying soil types and characteristics, shaping the landscape and ecosystems in which they exist.
Subsidence: Subsidence refers to the gradual sinking or settling of the Earth's surface, which can occur due to various natural and human-induced processes. This phenomenon is often associated with the removal of underground resources, such as water, oil, or minerals, leading to a decrease in support for surface structures. Subsidence can significantly affect landforms and ecosystems, particularly in relation to erosion processes and the broader geological stability of an area.
Surface Relief: Surface relief refers to the variation in elevation and contours of the Earth's surface, which can include mountains, valleys, plateaus, and plains. This term is essential for understanding how processes like uplift and subsidence shape the landscape over time, influencing everything from ecosystems to human activity.
Tectonic uplift: Tectonic uplift refers to the vertical elevation of the Earth's surface caused by tectonic forces, such as the movement of tectonic plates. This process can lead to the formation of mountains, plateaus, and other elevated landforms, impacting the surrounding landscape and influencing various geomorphic processes. Understanding tectonic uplift is essential for grasping how landforms are created and how they evolve over time.
Volcanic activity: Volcanic activity refers to the processes and phenomena associated with the eruption of magma from beneath the Earth's crust, resulting in the formation of volcanoes, lava flows, and various volcanic landforms. This activity not only shapes the landscape but also influences fluvial processes, drainage patterns, and geological formations through both eruptive and non-eruptive events.
William Morris Davis: William Morris Davis was an influential American geographer, geologist, and geomorphologist known for his pioneering work in the study of landforms and the processes that shape them. His concepts of the geographic cycle and landscape evolution laid the groundwork for modern geomorphology, connecting various Earth processes to the formation and alteration of the landscape over time.