Creation of Seafloor and Coastal Features http://www.history.com/shows/how-the-earth-was-made/videos/how-the-earth-was-made-ring-of-fire

Continental Margins

Terms to Know Continental margins- shallow water areas close to the continents Passive margins- continental margin that lacks a plate boundary and is marked by a low degree of tectonic activity, such as those typical of the Atlantic Ocean Active margin- continental margin marked by a high degree of tectonic activity, such as those typical of the Pacific Rim

Continental Shelf Flat zone extending from the shore beneath the ocean surface to a point at which a marked increase in slope angle occurs called the shelf break Made up of granitic continental crust so it is geologically part of the continent Found along continents however average width varies depending on the local geology and topography

Continental Slope Relatively steeply sloping surface lying seaward of the continental shelf The slope of the continental slope is affected by the type of margin present Passive margins have gentle slopes Convergent active margins have steep slopes due to the trenches

Continental Rise Gently sloping depositional surface at the base of the continental slope Turbidity currents that move through and erode submarine canyons transports material that exit the mouth of the canyon and settle deposit at the base of the continental slope Only found along passive margins, are NOT found along convergent active margins since continental slope leads to a trench

Abyssal Plain Flat depositional surface extending seaward from the continental rise or oceanic trenches Formed by fine particles of sediment slowly drifting onto the deep ocean floor Few occur in the Pacific most occur in the Atlantic and Indian Ocean (the convergent active margins in the Pacific prevent the sediment moving past the continental slope)

Seafloor Features

Ocean Ridges Long continuous mountain range on the sea floor Created by sea-floor spreading at divergent boundaries Examples: Mid-Atlantic Ridge, Pacific-Antarctic Ridge, Juan de Fuca Ridge

Generation of a Divergent Boundary

Ocean Ridge Video http://youtu.be/uSKzdbEVsI8

Hydrothermal Vent Sea-floor hot springs Created as cold seawater seeps down along cracks and fractures in the ocean crust is heated by underlying magma and surfaces again through these vents Found all along the mid-ocean ridge

Hydrothermal Vent

Hydrothermal Vent Video

Trenches Deep linear scars in the ocean floor Caused by the collision of two plates along convergent plate margins (continental-oceanic or oceanic-oceanic) Mariana Trench, Peru-Chile Trench, Aleutian Trench

Trenches from Oceanic-Oceanic Convergence

Trenches from Oceanic-Continental Convergence

Marianas Trench Video http://www.history.com/shows/how-the-earth-was-made/videos/deepest-place-on-earth

Ring of Fire—Depths Below

Underwater Volcanism

Deep Ocean Volcanoes

Seamount An individual volcanic peak extending over 1000 meters above the surrounding ocean floor Created due to volcanic activity either from activity at a mid-oceanic ridge, a hotspot, or oceanic-oceanic convergence Example: Hawaiian Islands-Emperor Seamount Chain

Island A piece of land completely surrounded by water Formed by volcanic activity West Indies, Antilles, Tobago, Fiji

Island Chain Group of islands formed by the same geological process Can either be formed as an oceanic plate moves over a hot spot, or at oceanic-oceanic convergence Hawaii (hot spots); Aleutian Islands (oceanic-oceanic convergence)

Guyout or Tablemount Seamount with a flat top As a seamount moves away from its magma source the top can be flattened due to wave action Ex: Gifford Guyot off the coast of New South Wales

Atoll Ring shaped coral reef surrounded by a lagoon Coral reef that formed around a volcano which remains and continues to grow after the volcano has subsided back into the ocean Ex: Bikini Atoll, Lighthouse reef, Motu Iti

Coastal Features http://app.discoveryeducation.com/player/view/assetGuid/69668 832-84CB-4C8E-8AF7-45F1B0F0ADA0

Peninsula A piece of land almost completely surrounded by water Formed by coastal erosion Ex: Florida, Italy

Delta Alluvial deposit at the mouth of the river Form from deposition of sediment carried by a river as the flow leaves its mouth. Ex: Mississippi River Delta

Submarine Canyon Deep canyon cut into the continental shelf and slope, often found at the mouth of a river Carved by turbidity currents created by rivers or deltas Ex: Alvies Canyon in the Bay of Biscay in Spain

Cape (Headland) Coastal landform that extends out into a body of water Formed by coastal erosion Ex: Cape Fear

Bay Inlet of the sea Formed as softer rock erodes while more resistant rock does not forming a headland Ex: Galveston Bay, Chesapeake Bay