North American Plate — Introduction
The North American Plate is a principal tectonic plate with an area of approximately 76 million km² (29 million mi²), making it the second-largest plate on Earth. Its surface encompasses most of the North American continent, Greenland, portions of northeastern Siberia, and several adjacent island territories including Cuba, the Bahamas, parts of Iceland and parts of the Azores. The plate’s eastern margin is defined by the seismically active Mid-Atlantic Ridge and extends to the Azores triple junction, where it meets the Eurasian and Nubian plates. To the west it reaches as far as the Chersky Range in eastern Siberia, giving the plate a transcontinental extent that links North America with extreme northeastern Asia; its principal oceanic neighbor to the west is the Pacific Plate, the largest tectonic plate.
Structurally, the plate comprises both continental and oceanic crust. The continental interior is underlain by a long-lived granitic craton that constitutes the stable basement of the continent. Flanking this craton are numerous accreted terranes—discrete crustal fragments added by successive episodes of collision and subduction. Much of the region west of the Rocky Mountains is dominated by these accreted terranes, reflecting a protracted tectonic history of repeated collisions, subduction processes, and terrane accretion that assembled the present continental margin.
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Boundaries
The southern margin of the North American Plate is largely characterized by lateral, transform‑fault motion where it interfaces with the Cocos Plate to the west and the Caribbean Plate to the east. Major transcurrent structures such as the Swan Islands Transform beneath the Caribbean Sea and the Motagua Fault across Guatemala accommodate much of the horizontal displacement between these plates. Along Hispaniola, two nearly parallel strike‑slip systems—the Septentrional and the Enriquillo–Plantain Garden faults—act as a paired boundary that defines the Gonâve microplate within the eastern Caribbean tectonic mosaic. North of Puerto Rico and the Virgin Islands the Puerto Rico Trench and its associated faults mark the northern plate limit and provide the principal bathymetric expression that bounds the Puerto Rico–Virgin Islands microplate.
Eastward toward the Mid‑Atlantic Ridge the plate’s southern transition to South America is not localized on a single fault but is diffuse, broadly situated near the Fifteen‑Twenty fracture zone around 16°N and representing a poorly defined zone of transition. In the Arctic the North American Plate is linked to oceanic spreading by the Gakkel Ridge, the high‑latitude continuation of the global Mid‑Atlantic Ridge, which functions as the chief divergent boundary in the far north.
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In the far northwestern sector the plate boundary evolves from oceanic spreading into continental deformation: the Laptev Sea Rift and the Chersky Range form a transitional deformation corridor, separated from the Okhotsk microplate by the Ulakhan Fault, before the boundary continues oceanward into the Aleutian Trench and terminates in the complex region of the Queen Charlotte Fault system and the Aleutian arc.
The western margin presents a mixture of transform and convergent regimes. Offshore Alaska the Queen Charlotte Fault and, to its south, the Cascadia subduction zone are key elements; farther south the San Andreas fault system transects California while the East Pacific Rise propagates into the Gulf of California. The Middle America Trench constitutes the principal convergent boundary along the plate’s southern Pacific margin.
These western features reflect a long history of subduction of the Farallon Plate beneath North America since the Jurassic. Progressive consumption of the Farallon has left fragmented remnants—Juan de Fuca, Explorer, Gorda, Rivera, Cocos and Nazca—which now occupy the northeast Pacific margin and control much of the contemporary oceanic‑continental interaction, including the present‑day Pacific–North American contact expressed by the San Andreas system. The Gulf of California Rift Zone, comprising rift basins and transform segments from the East Pacific Rise into the Salton Trough and Brawley seismic zone, records active continental rifting linked to northward propagation of the spreading center; whether the oceanic crust formed in this propagating system represents a distinct, independently behaving oceanic plate remains unresolved.
On the Mid‑Atlantic Ridge near the Azores triple junction, the islands of Flores and Corvo lie on the easternmost edge of the North American Plate, whereas most of the archipelago occupies African or Eurasian plates—an arrangement that underscores the triple‑junction complexity of plate and mantle interactions in this region.
Hotspots beneath the North American plate are expressed as discrete zones of localized volcanism and seismicity; principal examples include Yellowstone (Wyoming), the Jemez Lineament (New Mexico), and the Anahim field (British Columbia). These centers record ongoing surface manifestations of mantle thermal anomalies and, in the cases of Yellowstone and Anahim, a history of activity that began in the Miocene and persists today.
The dominant conceptual model interprets these features as the surface expression of mantle plumes—narrow, buoyant upwellings that ascend from the core–mantle boundary and provide a long-lived, focused heat source beneath the lithosphere. An alternative hypothesis attributes hotspot volcanism to processes confined to the upper mantle, with convective patterns there producing melt in more distributed or episodic ways; this upper-mantle view implies different spatial and temporal signatures of volcanism than a deep-plume origin.
Yellowstone is characterized by a Miocene-to-present track of caldera formation and rhyolitic volcanism, most conspicuously the Yellowstone Caldera and the chain of calderas along the Snake River Plain. The Anahim hotspot likewise initiated in the Miocene and built the Anahim Volcanic Belt, with recent activity concentrated near Nazko Cone. The Jemez Lineament is recognized as a major hotspot-related feature in the southwestern United States, contributing to regional volcanic and tectonic complexity.
Collectively, these systems demonstrate that mantle-sourced thermal anomalies beneath the North American plate generate persistent volcanism and earthquake activity; distinguishing between a deep plume and upper-mantle convection origin remains a central question for interpreting their spatial distribution and longevity.
The North American Plate is moving predominantly southwestward away from the Mid‑Atlantic Ridge at about 2.3 cm yr–1 (~1 in yr–1), consistent with ongoing seafloor spreading at that ridge. In contrast, the adjacent Pacific Plate translates northwestward much more rapidly—on the order of 7–11 cm yr–1 (~3–4 in yr–1)—creating a pronounced velocity gradient between the two plates.
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Because almost none of the North American Plate is currently being consumed by subduction (the Puerto Rico Trench provides a localized exception), classic slab‑pull cannot account for the plate’s overall motion. This absence of widespread subduction has prompted consideration of alternative driving forces; notably, a 2007 study argued that mantle convective flow beneath the lithosphere could supply the horizontal traction necessary to drive the plate.
The large difference in absolute speed and direction between North America and neighboring plates produces substantial relative motion that must be accommodated along plate boundaries and transform zones. Consequently, strain localization, complex faulting, and variable boundary kinematics are required to reconcile the disparate motions of adjacent plates.