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Hawaiian Trough
The Hawaiian Trough, otherwise known as the Hawaiian Deep, is a moat-like depression of the seafloor surrounding the Hawaiian Islands. The weight from the volcanic island chain depresses the plastic lithosphere that is already weakened by the underlying thermal hotspot, causing subsidence to occur. The location with the greatest rate of subsidence is directly above the hotspot and beneath the youngest and largest island (Hawai'i) with a rate of about per year. The flexure in the lithosphere caused by subsidence beneath the island chain, and in particular Hawai'i, creates uplift along the ocean floor surrounding the trough. The elevated ocean floor is known as the Hawaiian Arch. The Hawaiian Arch extends about above the surrounding ocean floor, and contains tilted coral reefs. The Hawaiian Trough is about deep and has a radius of about .Rees, B. A., Detrick, R. S., & Coakley, B. J. (1993). Seismic stratigraphy of the Hawaiian flexural moat. ''Geologic Society of America Bulletin' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moat
A moat is a deep, broad ditch dug around a castle, fortification, building, or town, historically to provide it with a preliminary line of defence. Moats can be dry or filled with water. In some places, moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer. Historical use Ancient Some of the earliest evidence of moats has been uncovered around ancient Egyptian fortresses. One example is at Buhen, a settlement excavated in Nubia. Other evidence of ancient moats is found in the ruins of Babylon, and in reliefs from ancient Egypt, Assyria, and other cultures in the region. Evidence of early moats around settlements has been discovered in many archaeological sites throughout Southeast Asia, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storm Surge
A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the normal tidal level, and does not include waves. The main meteorological factor contributing to a storm surge is high-speed wind pushing water towards the coast over a long fetch. Other factors affecting storm surge severity include the shallowness and orientation of the water body in the storm path, the timing of tides, and the atmospheric pressure drop due to the storm. As extreme weather becomes more intense and the sea level rises due to climate change, storm surges are expected to cause more risk to coastal populations. Communities and governments can adapt by building hard infrastructure, like surge barriers, soft infrastructure, like coastal dunes or mangroves, improving coastal construction practices and building social strat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of Hawaii
The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kure Atoll. Formerly called the Sandwich Islands by Europeans, the present name for the archipelago is derived from the name of its largest island, Hawaii. The archipelago sits on the Pacific Plate. The islands are exposed peaks of a great undersea mountain range known as the Hawaiian–Emperor seamount chain, formed by volcanic activity over the Hawaiian hotspot. The islands are about from the nearest continent and are part of the Polynesia subregion of Oceania. The U.S. state of Hawaii occupies the archipelago almost in its entirety (including the mostly uninhabited Northwestern Hawaiian Islands), with the sole exception of Midway Atoll (a United States Minor Outlying Island). Hawaii is the only U.S. state that is situated entirely on an archipelago, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Landslide
Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting stress of the seafloor slope material, causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings, including planes as low as 1°, and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology. Causes Submarine landslides have different causes which relate to both the geological attributes of the landslide material and transient environmental factors affecting the submarine environment. Common causes of landslides include: i) presence of weak geological layers, ii) overpressure due to rapid accumulati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Arch Volcanic Field
South Arch volcanic field is an underwater volcanic field south of Hawaiʻi Island. It was active during the last 10,000 years, and covers an area of at a depth of . Although the field is related to the Hawaiian hotspot, it does not appear to be a precursory volcano, but seems to have formed when the weight of the growing Hawaiian volcanoes caused the oceanic crust to buckle, opening up pathways for magma to ascend in front of the hotspot. Geomorphology The volcanic field lies about south from Hawaiʻi Island, at a depth of around below sea level. It covers an area of . It consists of several metres thick lava flows that are surrounded by sediment-covered seafloor mainly to the north and east and by clusters of Cretaceous seamounts mainly to the west and southwest. In sidescan sonar images, young lava flows have a bright appearance while older ones are covered by sediments and thus appear darker, and structures identified as lava coils, lava rubble, lava tumuli, pillow la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ʻAuʻau Channel
In an archipelago like the Hawaiian Islands the water between islands is typically called a ''channel'' or ''passage''. Described here are the channels between the islands of Hawaiʻi, arranged from northwest to southeast. Kaulakahi Channel The Kaulakahi Channel separates the islands of Niʻihau and Kauaʻi. It is wide. Kaulakahi translates to "the single flame (streak of color)." Kaʻieʻie Waho Channel The Kaʻieʻie Waho Channel, also called the Kauai Channel,The Road Atlas of United States, Canada & Mexico (Rand McNally, 2004) p. 30. separates the islands of Kauaʻi and Oʻahu, at a distance of . Kaʻieʻie Waho means "Outer Kaʻieʻie," named after the ʻieʻie vine (''Freycinetia arborea''). The maximum depth of the channel is over . Kaiwi Channel The Kaiwi Channel (also known as the Molokai Channel) separates the islands of Oʻahu and Molokaʻi, and is wide. Maximum depth is . ''Ka Iwi'' means "the bone." There are annual paddleboarding and outrigger canoe pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish
A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can be grouped into the more basal (phylogenetics), basal jawless fish and the more common jawed fish, the latter including all extant taxon, living cartilaginous fish, cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break to the long tradition of grouping all fish into a single Class (biology), class (Pisces), modern phylogenetics views fish as a paraphyletic group. Most fish are ectotherm, cold-blooded, their body temperature varying with the surrounding water, though some large nekton, active swimmers like white shark and tuna can hold a higher core temperature. Many fish can communication in aquatic animals#Acoustic, communicate acoustically with each other, such as during courtship displays. The stud ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesophotic Coral Reef
A mesophotic coral reef or mesophotic coral ecosystem (MCE), originally from the Latin word ''meso'' (meaning middle) and ''photic'' (meaning light), is characterized by the presence of both light-dependent coral and algae, and organisms that can be found in water with low light penetration. Mesophotic coral ecosystems occur at depths beyond those typically associated with coral reefs as the mesophotic ranges from brightly lit to some areas where light does not reach. Mesophotic coral ecosystem (MCEs) is a new, widely adopted term used to refer to mesophotic coral reefs, as opposed to other similar terms like "deep coral reef communities" and "twilight zone", since those terms sometimes are confused due to their unclear, interchangeable nature. Many species of fish and corals are endemic to the MCEs making these ecosystems a crucial component in maintaining global diversity. Recently, there has been increased focus on the MCEs as these reefs are a crucial part of the coral reef syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Wave
Internal waves are gravity waves that oscillate within a fluid medium, rather than on its surface. To exist, the fluid must be stratified: the density must change (continuously or discontinuously) with depth/height due to changes, for example, in temperature and/or salinity. If the density changes over a small vertical distance (as in the case of the thermocline in lakes and oceans or an atmospheric inversion), the waves propagate horizontally like surface waves, but do so at slower speeds as determined by the density difference of the fluid below and above the interface. If the density changes continuously, the waves can propagate vertically as well as horizontally through the fluid. Internal waves, also called internal gravity waves, go by many other names depending upon the fluid stratification, generation mechanism, amplitude, and influence of external forces. If propagating horizontally along an interface where the density rapidly decreases with height, they are specifically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Wasting
Mass wasting, also known as mass movement, is a general term for the movement of rock (geology), rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not Entrainment (physical geography), entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include Downhill creep, creep, solifluction, rockfalls, debris flows, and landslides, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, Jupiter's moon Io (moon), Io, and on many other bodies in the Solar System. Subsidence is sometimes regarded as a form of mass wasting. A distinction is then made between mass wasting by subsidence, which involves little horizontal movement, and mass wasting by slope movement. Rapid mass wasting events, such as landslides, ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depression (geology)
In geology, a depression is a landform sunken or depressed below the surrounding area. Depressions form by various mechanisms. Types Erosion-related: * Blowout (geomorphology), Blowout: a depression created by Aeolian processes, wind erosion typically in either a partially vegetated Dune, sand dune ecosystem or dry soils (such as a post-glacial loess environment). * Glacial valley: a depression carved by erosion by a glacier. * River valley: a depression carved by fluvial erosion by a river. * Area of subsidence caused by the collapse of an underlying structure, such as sinkholes in karst terrain. * Sink (geography), Sink: an endorheic depression generally containing a wikt:persistent, persistent or intermittent (seasonal) lake, a Salt pan (geology), salt flat (playa) or dry lake, or an ephemeral lake. * Panhole: a shallow depression or basin eroded into flat or gently sloping, cohesive rock.Twidale, C.R., and Bourne, J.A., 2018Rock basins (gnammas) revisited.''Géomorphologie: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age). Historical development Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
