2.2 Types of plate boundaries: divergent, convergent, and transform
4 min read•august 16, 2024
Plate boundaries are where tectonic plates meet, shaping Earth's surface. These zones come in three types: divergent (plates move apart), convergent (plates collide), and transform (plates slide past each other). Each type creates unique landforms and geological processes.
Understanding plate boundaries is key to grasping Earth's dynamic nature. They explain why we have mountains, , and . By studying these boundaries, scientists can better predict geological events and understand our planet's past and future.
Plate Boundary Types
Classification and Characteristics of Plate Boundaries
Top images from around the web for Classification and Characteristics of Plate Boundaries
What Type of Plate Boundary? – Physical Geology Laboratory View original
Is this image relevant?
Sea Floor Spreading | Physical Geography View original
Is this image relevant?
Motion at Plate Boundaries – Physical Geology Laboratory View original
Is this image relevant?
What Type of Plate Boundary? – Physical Geology Laboratory View original
Is this image relevant?
Sea Floor Spreading | Physical Geography View original
Is this image relevant?
1 of 3
Top images from around the web for Classification and Characteristics of Plate Boundaries
What Type of Plate Boundary? – Physical Geology Laboratory View original
Is this image relevant?
Sea Floor Spreading | Physical Geography View original
Is this image relevant?
Motion at Plate Boundaries – Physical Geology Laboratory View original
Is this image relevant?
What Type of Plate Boundary? – Physical Geology Laboratory View original
Is this image relevant?
Sea Floor Spreading | Physical Geography View original
Is this image relevant?
1 of 3
- Plate boundaries form zones where tectonic plates interact resulting in various geological processes and landforms
- Three main types of plate boundaries exist based on relative plate motion and crust type (oceanic or continental)
- Divergent boundaries occur where two plates move away from each other creating new crust
- Convergent boundaries form where two plates move towards each other resulting in or collision
- Transform boundaries develop where two plates slide past each other horizontally with no creation or destruction of crust
- Plate boundary classification depends on:
- Relative motion of the plates involved
- Type of crust at the boundary (oceanic or continental)
Specific Plate Boundary Examples
- examples:
- Mid-Atlantic Ridge (oceanic setting)
- East African Rift System (continental setting)
- examples:
- Mariana (oceanic-oceanic subduction)
- Himalayas ()
- examples:
- San Andreas Fault (continental transform)
- Fracture zones offsetting segments (oceanic transform)
Geological Processes at Plate Boundaries
Divergent Boundary Processes
- Characterized by forming new oceanic crust
- Rift valley formation in continental settings
- Processes involved:
- Upwelling of magma from the mantle
- Cooling and solidification of magma to form new crust
- Extensional forces causing thinning and rifting of existing crust
- Associated features:
- Mid-ocean ridges (underwater mountain ranges)
- Rift valleys (elongated depressions)
- Volcanic activity (basaltic lava flows)
Convergent Boundary Processes
- Subduction occurs where one plate descends beneath another (typically oceanic under continental or oceanic)
- Continental collision happens when two continental plates meet
- Subduction zone processes:
- Formation of deep oceanic trenches
- Development of volcanic arcs (island arcs or continental volcanic belts)
- Creation of accretionary wedges (sediment accumulation)
- Metamorphism of subducted materials
- Continental collision processes:
- Extensive mountain building (orogeny)
- Crustal thickening and deformation
- Metamorphism of rocks due to high pressure and temperature
Transform Boundary Processes
- Associated with strike-slip causing horizontal displacement
- Processes and features:
- Offset of geological features (rivers, rock formations)
- Generation of shallow frequent earthquakes
- Development of linear fault zones
- Minimal vertical relief but significant horizontal movement
- Transform faults also occur as fracture zones offsetting mid-ocean ridge segments
Plate Boundary Comparisons
Forces and Motions at Boundaries
- Divergent boundaries experience extensional forces pulling plates apart
- Convergent boundaries dominated by compressional forces pushing plates together
- Transform boundaries undergo shear forces as plates slide past each other
- Plate motion rates vary among boundary types:
- Divergent boundaries typically move slower (few cm/year)
- Convergent and transform boundaries often move faster (up to 10 cm/year or more)
Resulting Landforms and Features
- Divergent boundaries create:
- Rift valleys in continental settings (East African Rift)
- Mid-ocean ridges in oceanic settings (Mid-Atlantic Ridge)
- Convergent boundaries form:
- Mountain ranges (Andes Mountains)
- Volcanic arcs (Ring of Fire)
- Deep ocean trenches (Mariana Trench)
- Transform boundaries produce:
- Linear fault zones (San Andreas Fault)
- Offset features with little vertical relief
- Crust type influence on landforms:
- Oceanic-oceanic convergence leads to island arcs (Japan)
- Continental-continental convergence results in large mountain ranges (Himalayas)
Driving Forces of Plate Motion
Primary Driving Mechanisms
- Mantle convection acts as the primary driving force behind
- Creates upwelling and downwelling currents moving the overlying plates
- Convection cells transport heat from Earth's interior to the surface
- Ridge push at divergent boundaries occurs due to:
- Elevation difference between the ridge and older cooler denser oceanic crust
- Gravitational potential energy of the elevated ridge
- Slab pull at convergent boundaries caused by:
- Negative buoyancy of cold dense subducting plate sinking into the mantle
- Considered the dominant force in plate tectonics
Secondary Forces and Influences
- Gravitational sliding (trench suction) contributes to plate motion at convergent boundaries
- Subducting plate pulls the overriding plate towards the trench
- Frictional forces at transform boundaries resist plate motion
- Overall maintained by forces acting on other plate boundaries
- Complex patterns of global plate motions determined by:
- Balance of driving and resisting forces
- Variations in mantle viscosity
- Differences in plate strength and thickness
- Other factors influencing plate motion:
- Tidal forces (minor effect)
- Earth's rotation (Coriolis effect on large-scale mantle flow)
Key Terms to Review (24)
Alfred Wegener: Alfred Wegener was a German meteorologist and geophysicist known for proposing the theory of continental drift in the early 20th century. His ideas laid the groundwork for modern plate tectonics by suggesting that continents were once joined together in a single landmass called Pangaea and have since drifted apart. This theory challenged existing geological beliefs and sparked further research into the mechanisms of plate movement and the formation of geological features.
Continental Drift: Continental drift is the theory that continents have moved slowly over geological time from their original positions to their current locations. This concept helps explain the formation of continents and ocean basins, as well as the distribution of various geological features and living organisms across the globe.
Continental-continental collision: A continental-continental collision occurs when two tectonic plates, both composed of continental crust, converge and push against each other. This type of collision results in the formation of mountain ranges and significant geological uplift as the crust buckles and folds, showcasing the immense forces at play in Earth's tectonic processes.
Convergent Boundary: A convergent boundary is a tectonic plate boundary where two plates move toward each other, often resulting in one plate being forced beneath the other in a process known as subduction. This interaction leads to significant geological features and phenomena, including earthquakes, volcanic activity, and mountain building, reflecting the dynamic nature of Earth's lithosphere.
Divergent boundary: A divergent boundary is a tectonic plate boundary where two plates move away from each other, allowing magma from the mantle to rise and create new crust. This process plays a crucial role in the formation of ocean basins and rift valleys, contributing to the geological features and topography of Earth.
Earthquakes: Earthquakes are sudden releases of energy in the Earth's crust, resulting from tectonic movements that create seismic waves. These movements can occur at different types of plate boundaries, affecting geological formations and human structures alike, and they are often linked to various geological processes such as subduction, rifting, and faulting.
Faulting: Faulting refers to the process of fracturing and displacement of rocks within the Earth's crust, often resulting from tectonic stress. This process is a key mechanism in the generation of earthquakes, forming along different types of faults, and plays a crucial role in shaping geological features such as mountains and valleys.
Harry Hess: Harry Hess was a prominent American geologist and a key figure in the development of the theory of plate tectonics, particularly known for his contributions to understanding seafloor spreading. His work helped establish the mechanisms of plate movement and the formation of ocean basins, connecting various geological features and processes within the Earth's lithosphere.
Lateral sliding: Lateral sliding refers to the horizontal movement of tectonic plates past one another along transform plate boundaries. This type of motion is characterized by plates sliding side by side, which can lead to significant geological activity, including earthquakes. The interaction between these plates can create stress and friction, resulting in the release of energy in the form of seismic waves when they finally slip.
Mid-ocean ridge: A mid-ocean ridge is an underwater mountain range formed by plate tectonics, where two tectonic plates are moving apart, allowing magma to rise and create new oceanic crust. These ridges are significant features of ocean basins, influencing the formation of continents and shaping the seafloor through processes like seafloor spreading.
Mountain range: A mountain range is a series of connected mountains, often formed by geological processes such as tectonic plate movements. These ranges typically arise in regions where tectonic forces create uplift and folding of the Earth's crust, leading to significant changes in topography and influencing both natural landscapes and human activities.
Normal fault: A normal fault is a type of geological fault where the hanging wall moves downward relative to the footwall due to extensional forces. This movement occurs as a result of tectonic activity, often at divergent plate boundaries where plates are moving apart, allowing for the formation of rift valleys and other geological features. Normal faults are crucial for understanding how the Earth's crust can stretch and fracture in response to tectonic stresses.
Oceanic-continental convergence: Oceanic-continental convergence is a tectonic process where an oceanic plate collides with a continental plate, leading to significant geological features and events. This type of boundary is crucial in the formation of mountain ranges and volcanic activity, showcasing the dynamic nature of Earth's lithosphere as these two different types of plates interact.
Plate movement: Plate movement refers to the continuous motion of Earth's lithospheric plates due to the convection currents in the underlying asthenosphere. This movement leads to various geological processes and interactions, which include the formation of mountains, earthquakes, and volcanic activity, all of which are influenced by different types of plate boundaries.
Plate Tectonics: Plate tectonics is the scientific theory that explains the movement and interaction of Earth's lithosphere, which is divided into several large, rigid plates that float on the semi-fluid asthenosphere beneath. This theory helps explain a variety of geological phenomena, including the formation of continents, ocean basins, mountain ranges, and earthquakes, all of which are crucial for understanding Earth's dynamic processes.
Reverse fault: A reverse fault is a type of fault where the hanging wall moves up relative to the footwall due to compressional forces. This movement occurs when tectonic plates collide or converge, pushing rock layers together and causing one side to be thrust over the other. Reverse faults are often found in mountain ranges and are a key feature of fold and thrust belts, showcasing how tectonic activity shapes the Earth's crust.
Seafloor Spreading: Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges as tectonic plates move apart. This geological phenomenon plays a crucial role in the formation of ocean basins and influences various tectonic activities, including the generation of rift valleys and the distribution of magnetic anomalies on the seafloor.
Strike-slip fault: A strike-slip fault is a type of fault where two blocks of crust slide past one another horizontally, with minimal vertical movement. This lateral movement occurs due to shear stress, primarily associated with transform plate boundaries, leading to significant geological features and seismic activity.
Subduction: Subduction is the geological process where one tectonic plate moves under another and sinks into the mantle as the plates converge. This process is crucial in shaping Earth’s features, influencing everything from the formation of oceanic trenches to the creation of mountain ranges and volcanic activity.
Tectonic cycle: The tectonic cycle refers to the continuous movement and interaction of Earth's lithospheric plates, which results in various geological processes such as the formation of mountains, earthquakes, and volcanic activity. This cycle includes processes like plate tectonics, subduction, and rifting, connecting it to different types of plate boundaries and their impacts on Earth's surface and interior.
Transform boundary: A transform boundary is a type of tectonic plate boundary where two plates slide past each other horizontally. This movement creates friction and can lead to significant seismic activity, often resulting in earthquakes, as the plates get stuck and release energy suddenly when they finally move.
Trench: A trench is a deep, elongated depression in the ocean floor, typically formed at convergent plate boundaries where one tectonic plate is subducted beneath another. These features are significant in shaping ocean basins and continents and are closely tied to processes such as earthquake generation, volcanic activity, and the overall dynamics of plate tectonics.
Tsunamis: Tsunamis are large ocean waves generated by significant disturbances in or near a body of water, most commonly caused by underwater earthquakes, volcanic eruptions, or landslides. These waves can travel across entire ocean basins and cause devastating effects when they reach coastlines, making them an important consideration in the context of geological activities and plate interactions.
Volcanoes: Volcanoes are geological formations that occur when molten rock, ash, and gases escape from beneath the Earth's crust, creating eruptions. They are closely linked to the movement of tectonic plates and play a crucial role in shaping landscapes and influencing ecosystems.