Oceanography exam 1
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196 Terms
What are Earth's four principal oceans?
Pacific, Atlantic, Indian, and Arctic Oceans. The Southern Ocean is also recognized as a major ocean surrounding Antarctica.
Which is the largest ocean?
Pacific Ocean. It covers more area than all of Earth's land area combined.
Which is the second-largest ocean?
Atlantic Ocean.
Which is the third-largest ocean?
Indian Ocean.
Which is the smallest principal ocean?
Arctic Ocean.
Where is the Pacific Ocean located?
Between Asia/Australia and North/South America.
Where is the Atlantic Ocean located?
Between the Americas and Europe/Africa.
Where is the Indian Ocean located?
Between Africa, Asia, Australia, and Antarctica.
Where is the Arctic Ocean located?
Around the North Pole, surrounded primarily by North America, Europe, and Asia.
What is the deepest ocean trench?
The Mariana Trench, located in the western Pacific Ocean.
What is the deepest known point in the Mariana Trench?
Challenger Deep, roughly 11 km (about 36,000 ft) below sea level.
How was the Mariana Trench explored by humans?
The deepest area has been reached by manned and unmanned submersibles. Don Walsh and Jacques Piccard first reached Challenger Deep in 1960 aboard the Trieste.
What did early Pacific Islanders contribute to ocean exploration?
They developed advanced navigation techniques, using stars, waves, winds, currents, clouds, birds, and other environmental clues to navigate across huge distances.
When did early Pacific Islander exploration occur?
Approximately 4000 BC–900 AD, with extensive settlement and exploration across the Pacific.
What was the Kon-Tiki voyage?
A 1947 expedition led by Thor Heyerdahl in which he sailed from South America toward Polynesia on a balsa-wood raft.
Why was the Kon-Tiki voyage important?
Heyerdahl wanted to demonstrate that ancient people could potentially have traveled across the Pacific on relatively simple rafts. It demonstrated feasibility, not that this was necessarily how Polynesia was settled.
Who were the Phoenicians?
An ancient seafaring civilization from the eastern Mediterranean known for trade, navigation, and exploration.
What important ocean exploration accomplishment is associated with the Phoenicians?
A Phoenician expedition is traditionally credited with circumnavigating Africa, although the historical account is debated.
Who was Pytheas?
A Greek explorer who traveled into the northern Atlantic and described places including Britain and possibly areas near Iceland.
What did the Greeks contribute to ocean exploration?
They improved knowledge of geography, navigation, tides, winds, and ocean currents.
What did the Romans contribute to ocean exploration?
They expanded Mediterranean navigation, trade, mapping, and knowledge of coastal waters.
What happened to European ocean exploration during much of the Middle Ages?
Long-distance European exploration declined compared with the Roman period, although Arab, Viking, and other sailors continued important exploration and trade.
Who were the Vikings?
Seafaring peoples from Scandinavia who explored and settled areas including Iceland, Greenland, and North America.
What was significant about Viking exploration?
Vikings reached North America centuries before Columbus, including the settlement at L'Anse aux Meadows.
Who was Zheng He?
A Chinese admiral during the Ming Dynasty who commanded enormous voyages across the Indian Ocean.
Why were Zheng He's voyages important?
They expanded Chinese knowledge and diplomatic/trade connections throughout the Indian Ocean and surrounding regions.
Who was Christopher Columbus?
A European explorer who sailed across the Atlantic in 1492 under the sponsorship of Spain.
What did Columbus believe he was accomplishing?
He was attempting to find a westward route to Asia.
What was the major result of Columbus's voyages?
They initiated sustained European contact, conquest, colonization, and exchange between the Americas and Europe.
Who was John Cabot?
An Italian-born explorer sailing for England who reached the North American coast in 1497, likely somewhere in the region of Atlantic Canada.
Who was Ferdinand Magellan?
A Portuguese explorer who led the expedition that became the first expedition to circumnavigate Earth.
Did Magellan personally complete the circumnavigation?
No. Magellan was killed in the Philippines. His expedition continued under other leaders and eventually completed the voyage.
Why was Magellan's expedition important to oceanography?
It provided extensive information about Earth's oceans, geography, distances, and global interconnectedness.
Who was Fridtjof Nansen?
A Norwegian explorer, scientist, and oceanographer known for Arctic exploration and important oceanographic research.
What was the Nansen bottle?
A device used to collect seawater samples from specific depths.
How did a Nansen bottle work?
The bottle was lowered to a desired depth. A messenger traveled down the wire and triggered the bottle to close, trapping water from that depth.
Why was the Nansen bottle important?
It allowed scientists to study temperature, salinity, and other properties of seawater at different depths.
What is the nebular hypothesis?
The hypothesis that the solar system formed from a rotating cloud of gas and dust, called a solar nebula.
What happened to the solar nebula?
Gravity caused the material to collapse inward and rotate faster, forming a flattened disk.
What formed at the center of the nebula?
The Sun formed from concentrated material at the center.
How did planets form?
Dust and rock particles collided and stuck together through accretion, eventually forming larger bodies called planetesimals and then planets.
What is Protoearth?
The early developing Earth before it became the differentiated, relatively stable planet we know today.
How was Protoearth different from modern Earth?
Protoearth was much hotter, had intense volcanic activity, frequent impacts, and had not yet developed Earth's modern layered structure and atmosphere/oceans.
What caused Earth's density stratification?
As early Earth became hot and partially molten, gravity caused denser materials to sink toward the center while less-dense materials rose.
What are Earth's three major chemical layers?
Crust, mantle, and core.
What is Earth's crust?
The thin, outermost solid layer of Earth.
What is the mantle?
The thick layer between the crust and core, composed primarily of silicate minerals rich in iron and magnesium.
What is the core?
Earth's innermost layer, composed primarily of iron and nickel.
Which is Earth's densest layer?
The core.
What is the lithosphere?
The rigid outer layer of Earth, consisting of the crust plus the uppermost mantle.
What is the asthenosphere?
A hot, weaker, ductile layer of the upper mantle beneath the lithosphere.
How are the lithosphere and asthenosphere different?
Lithosphere = rigid
Asthenosphere = weaker and able to flow slowly
What moves on the asthenosphere?
Lithospheric/tectonic plates.
How does continental crust differ from oceanic crust?
Continental crust is generally thicker, less dense, and more granitic, while oceanic crust is generally thinner, denser, and more basaltic.
Which type of crust is older?
Generally continental crust because oceanic crust is continually recycled at subduction zones.
Which type of crust is denser?
Oceanic crust.
Which type of crust is thicker?
Continental crust.
How did Earth's initial atmosphere form?
Early gases were released primarily through volcanic outgassing, along with gases contributed by impacts and other processes.
What gases were important in the early atmosphere?
Water vapor, carbon dioxide, nitrogen, and other volcanic gases. Free oxygen was essentially absent.
How did Earth's oceans form?
As Earth cooled, water vapor condensed into liquid water. Additional water may have been delivered by water-rich asteroids and possibly comets.
Where did salts in the ocean come from?
Major sources include chemical weathering of rocks on land, rivers carrying dissolved ions to the ocean, volcanic/hydrothermal activity, and reactions between seawater and rocks.
Why is the ocean salty?
Dissolved ions accumulate in seawater through processes that add ions faster than they are permanently removed.
What is radiometric dating?
A method of determining the age of rocks or materials by measuring the decay of radioactive isotopes.
What is a half-life?
The amount of time required for half of a radioactive parent isotope to decay.
What is the estimated age of Earth?
Approximately 4.54 billion years.
Why is radiometric dating important?
It provides evidence for Earth's very old age and allows scientists to estimate the ages of rocks and geological events.
What was Alfred Wegener's theory?
Continental drift—the idea that continents were once joined and later moved apart.
What was Pangaea?
A supercontinent containing nearly all Earth's present-day continents.
What evidence did Wegener use for continental drift?
Four major pieces of evidence:
Continental fit
Matching rock sequences
Past glacial evidence
Matching fossils
What is continental fit?
The observation that continents, especially South America and Africa, appear to fit together like pieces of a puzzle.
What rock evidence supported Wegener?
Similar rock types, ages, and geological structures were found on continents now separated by oceans.
How did glacial evidence support continental drift?
Glacial deposits and scratches were found in areas that are currently tropical, suggesting those continents were once located closer to the poles.
How did fossils support continental drift?
Identical fossils were found on continents now separated by oceans, suggesting those continents were once connected.
Why was Wegener's theory initially rejected?
Wegener could not adequately explain what force could move entire continents.
What is plate tectonics?
The modern theory that Earth's lithosphere is divided into moving plates that interact at their boundaries.
How is plate tectonics different from continental drift?
Continental drift focused on moving continents. Plate tectonics explains that entire lithospheric plates move, carrying continents and oceanic crust.
What are magnetic polarity reversals?
Times when Earth's magnetic field reverses, causing magnetic north and south to switch.
What are seafloor magnetic anomalies?
Alternating bands of normal and reversed magnetic polarity recorded in oceanic crust.
How do magnetic stripes support seafloor spreading?
The stripes are symmetrical on either side of mid-ocean ridges, showing that new crust forms at the ridge and moves outward.
What is seafloor spreading?
The process in which new oceanic crust forms at mid-ocean ridges and moves away from the ridge.
What is heat flow?
The amount of heat escaping from Earth's interior through its surface.
How does uneven heat flow support plate tectonics?
Heat flow is especially high near mid-ocean ridges, where hot mantle rises and new crust forms.
How does earthquake distribution support plate tectonics?
Earthquakes are concentrated along plate boundaries, especially at subduction zones, mid-ocean ridges, and transform faults.
What is a divergent boundary?
A boundary where two plates move apart.
What forms at divergent boundaries?
Mid-ocean ridges, rift valleys, volcanic activity, and new crust.
What is a convergent boundary?
A boundary where two plates move toward each other.
What happens when oceanic crust meets continental crust?
The denser oceanic plate subducts beneath the continental plate.
What features can occur at convergent boundaries?
Trenches, volcanoes, earthquakes, mountain ranges, and subduction zones.
What is a transform boundary?
A boundary where plates slide horizontally past one another.
What is commonly associated with transform boundaries?
Earthquakes and transform faults.
What is a mantle plume?
A column of hot, rising mantle material.
What is a hot spot?
A relatively stationary area of volcanic activity associated with abnormally hot mantle material.
How can hot spots provide evidence for plate movement?
As a plate moves over a relatively stationary hot spot, it can create a chain of volcanoes showing the direction and approximate history of plate movement.
What is bathymetry?
The measurement and mapping of ocean depth and seafloor topography.
How did early navigators estimate ocean depth?
They used weighted lines or sounding lines lowered from ships until they reached the seafloor.
What is a hypsographic curve?
A graph showing the percentage/area of Earth's surface at different elevations and depths.
What does a hypsographic curve show?
It illustrates the distribution of continents above sea level and ocean basins below sea level.
What are the three major marine provinces?
Continental margins
Deep-ocean basins
Mid-ocean ridges
What is a continental margin?
The region where continental crust transitions into oceanic crust.
What is a deep-ocean basin?
The large area between the continental margins and mid-ocean ridges, including abyssal plains, trenches, and seamounts.