5.2 Tectonic and Structural Landforms

Tectonic and structural landforms shape Earth's surface through plate movements and crustal deformation. These processes create mountains, volcanoes, and rift valleys, influencing the landscape we see today.

Understanding these landforms is crucial in geomorphology, as they form the foundation for other erosional and depositional processes. Tectonic activity continues to shape our planet, impacting both natural systems and human societies.

Plate Tectonics and Landforms

Plate Tectonics Theory

Top images from around the web for Plate Tectonics Theory

• 

  Applications: Plate Tectonics – Physical Geology Laboratory View original

  Is this image relevant?

• 

  File:Tectonic plate boundaries.png - Wikipedia View original

  Is this image relevant?

• 

  Motion at Plate Boundaries – Physical Geology Laboratory View original

  Is this image relevant?

• 

  Applications: Plate Tectonics – Physical Geology Laboratory View original

  Is this image relevant?

• 

  File:Tectonic plate boundaries.png - Wikipedia View original

  Is this image relevant?

1 of 3

Top images from around the web for Plate Tectonics Theory

• 

  Applications: Plate Tectonics – Physical Geology Laboratory View original

  Is this image relevant?

• 

  File:Tectonic plate boundaries.png - Wikipedia View original

  Is this image relevant?

• 

  Motion at Plate Boundaries – Physical Geology Laboratory View original

  Is this image relevant?

• 

  Applications: Plate Tectonics – Physical Geology Laboratory View original

  Is this image relevant?

• 

  File:Tectonic plate boundaries.png - Wikipedia View original

  Is this image relevant?

1 of 3

• Plate tectonics is the theory that Earth's lithosphere is divided into several large, rigid plates that move and interact with each other, driven by convection currents in the mantle
• The boundaries between tectonic plates are sites of intense geologic activity, including earthquakes, volcanic eruptions, and mountain building

Types of Plate Boundaries

• Divergent boundaries occur where two plates move away from each other, causing rifting, seafloor spreading, and the formation of mid-ocean ridges (East Pacific Rise) and rift valleys (East African Rift)
• Convergent boundaries occur where two plates collide, resulting in subduction (one plate diving beneath another), leading to the formation of deep-ocean trenches (Mariana Trench), volcanic arcs (Aleutian Islands), and mountain ranges (Andes)
• Transform boundaries occur where two plates slide past each other horizontally, creating strike-slip faults (San Andreas Fault) and causing earthquakes

Tectonic Landform Characteristics

Mountain Types

• Fold mountains, such as the Himalayas and the Alps, form at convergent boundaries where two continental plates collide, causing the crust to thicken and uplift
• Volcanic arc mountains, such as the Andes and the Cascades, form at convergent boundaries where an oceanic plate subducts beneath a continental plate, leading to magma generation and volcanic eruptions

Volcano Types

• Shield volcanoes, such as Mauna Loa (Hawaii) and Olympus Mons (Mars), are formed by the accumulation of fluid basaltic lava flows and are associated with hot spots or divergent boundaries
• Stratovolcanoes, such as Mount Fuji (Japan) and Mount St. Helens (USA), are steep-sided, conical volcanoes formed by the accumulation of alternating layers of lava, ash, and pyroclastic material at subduction zones

Rift Valleys

• Rift valleys, such as the East African Rift and the Rio Grande Rift, are elongated depressions formed by the stretching and thinning of the lithosphere at divergent boundaries
  • Rift valleys are characterized by deep, steep-sided walls, a central valley floor, and associated volcanic (Kilimanjaro) and seismic activity
  • Examples of rift valleys include the Baikal Rift Valley (Russia) and the Rhine Graben (Germany)

Crustal Deformation and Earth's Surface

Faulting

• Faults are fractures in the Earth's crust along which movement has occurred, displacing rock layers on either side of the fault plane
  • Normal faults form under tensional stress, causing the hanging wall to move downward relative to the footwall, creating horsts and grabens (Basin and Range Province, USA)
  • Reverse faults form under compressional stress, causing the hanging wall to move upward relative to the footwall, often associated with mountain building (Himalayan Frontal Thrust)
  • Strike-slip faults form under shear stress, causing rock layers to slide horizontally past each other, as seen along transform boundaries (Dead Sea Transform)

Folding

• Folds are bends or warps in rock layers that form when the crust is compressed, causing the rocks to buckle and deform
  • Anticlines are upward-arching folds, while synclines are downward-arching folds
  • The orientation and geometry of folds can provide information about the direction and magnitude of the stress that caused the deformation
  • Examples of folded landscapes include the Jura Mountains (France/Switzerland) and the Appalachian Mountains (USA)

Ductile Deformation

• Ductile deformation occurs when rocks are subjected to high temperatures and pressures, causing them to flow and deform without fracturing, as in the formation of metamorphic rock
• Examples of ductile deformation include the formation of gneiss (Acasta Gneiss, Canada) and schist (Moine Thrust Belt, Scotland) in metamorphic terranes

Tectonic Activity's Impact

Earthquakes

• Earthquakes can cause significant damage to buildings, roads, and other infrastructure, leading to loss of life, injuries, and economic disruption
  • The severity of earthquake damage depends on factors such as magnitude, depth, distance from the epicenter, and local geology and construction practices
  • Seismic hazard maps and building codes are used to assess risk and mitigate potential damage in earthquake-prone areas (San Francisco, California)
  • Notable earthquakes include the 1906 San Francisco earthquake and the 2011 Tōhoku earthquake and tsunami (Japan)

Volcanic Eruptions

• Volcanic eruptions can pose threats to nearby populations through lava flows, pyroclastic flows, ash fall, and lahars (volcanic mudflows)
  • Volcanic ash can cause respiratory problems, disrupt air travel (2010 Eyjafjallajökull eruption, Iceland), and damage crops and infrastructure
  • Monitoring volcanic activity and establishing evacuation plans are crucial for reducing the impact of volcanic hazards on human populations (Mount Vesuvius, Italy)
  • Significant volcanic eruptions include the 79 AD eruption of Mount Vesuvius (Pompeii) and the 1980 eruption of Mount St. Helens (USA)

Slow Tectonic Processes

• Slow tectonic processes, such as subsidence and uplift, can affect coastal communities by altering sea levels and increasing the risk of flooding or erosion (Venice, Italy)
• Tectonic activity can also influence the distribution and availability of natural resources, such as minerals (Andean copper deposits), geothermal energy (Iceland), and groundwater (Great Artesian Basin, Australia), which can have both positive and negative impacts on human populations
• Understanding the relationship between tectonic processes and landscape evolution is essential for effective land-use planning, natural hazard mitigation, and resource management