OCN 150 History of the Ocean

marine chronograph

a highly accurate timekeeping device essential for determining longitude at sea by establishing the difference between local time and a reference time

nebular hypothesis

the scientific theory explaining the formation of the solar system from a rotating cloud of gas and dust called a nebula

nebula

a cloud of gases (mainly hydrogen and helium) and space dust in interstellar space

lithosphere

the rigid outer layer of the Earth, consisting of the crust and upper mantle

Asthenosphere

the ductile, semi-fluid layer of the upper mantle below the lithosphere

Mesosphere

the solid, lower part of the mantle, between the asthenosphere and the outer core

Outer Core

a liquid layer of the Earth’s core, primarily iron and nickel

Inner Core

the solid, innermost layer of the Earth’s core, primarily iron and nickel

oceanic crust

the thinner, denser crust that makes up the ocean floor, primarily basaltC

continental crust

the thicker, less dense crust that forms the continents, primarily granite

Stanley Miller’s Experiment

a 1952 experiment demonstrating that organic molecules (like amino acids) could spontaneously form from inorganic compounds under conditions thought to resemble early Earth

radiometric age dating

a method of dating geological or archaeological specimens by determining the relative proportions of particular radioactive isotopes present in a sample

half-life

the time required for half of the atoms of a radioactive substance to decay

geologic time scale

a system of chronological dating that relates geological stratigraphy to time, used by geologists to describe the timing and relationships of events that have occurred throughout Earth’s history

apparent polar wandering

the perceived moment over geologic time of Earth’s magnetic poles relative to the continents, which was later understood to be caused by the actual movement of the continents

asthenosphere

the ductile, semi-fluid layer of the Earth’s upper mantle, below the lithosphere, on which the tectonic plates float and move

continental drift

Alfred Wegener’s hypothesis that Earth’s continents have moved slowly over Earth’s surface through geologic time

Geologic Time Scale

a system of chronological dating that relates geological strata to time, used to describe the timing and relationships of events that have occurred throughout Earth’s history

lithosphere

The rigid outermost shell of a rocky planet, consisting of the crust and the uppermost part of the mantle. It is broken into tectonic plates.

magnetic anomalies

regular, symmetrical patterns of alternating stronger and weaker magnetic fields recorded in the rocks of the ocean floor, parallel to mid-ocean ridges, indicative of seafloor spreading and magnetic polarity reversals

magnetic dip

The angle that a magnetic mineral, such as magnetite, in an igneous or sedimentary rock aligns with Earth’s magnetic field at the time of the rock’s formation. This angle carries with latitude.

Magnetic Polarity Reversals

events in which the Earth’s magnetic field reverses direction, so that the positions of the magnetic North and South poles are interchanged. These reversals are recorded in seafloor rocks.

Magnetite

a common iron oxide mineral that is strongly magnetic and capable of recording Earth’s magnetic field when it crystallizes from magma

Magnetometer

an instrument used to measure the strength and direction of a magnetic filed, commonly towed behind ocean vessels to study the magnetism of seafloor rocks

mantle convection cells

the slow, churning currents within Earth’s mantle, where hot material rises and cooler material sinks, believed to be the primary driving force behind plate tectonics

Mid-Ocean Ridge

An underwater mountain range, typically having a rift valley at its crest, which is formed by the spreading of oceanic crust as magma rises from the mantle. It is a major site of seafloor spreading.

Paleomagnetism

The study of the record of Earth’s magnetic field in rocks, sediments, or archaeological materials. It helps determine the relative movement of continents and the age of ocean basins.

Pangaea

the supercontinent proposed by Alfred Wegener, which he believed existed approximately 200 million years ago and later broke apart to form the present continents

Panthalassa

The vast global ocean that surrounded the supercontinent Pangaea, according to Wegener’s hypothesis

Plate tectonics

The overarching scientific theory that describes the large-scale motion of Earth’s lithosphere. It explains how major landforms are created as a result of Earth’s subterranean forces.

Radiometric Dating

a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. It’s crucial for determining the age of ocean floor rocks.

Rift Valley

a linear low-lying area where the Earth’s crust has been pulled apart, often found at the crest of mid-ocean ridges or within continental landmasses

Seafloor Spreading

The process by which new oceanic crust is formed through volcanic activity at mid-ocean ridges and then gradually moves away from the ridge. This concept, proposed by Harry Hess, provided the missing mechanism for continental drift. S

SONAR

A technique that uses sound propagation to navigate, communicate with, or detect objects on or under the surface of the water, and has contributed to mapping the ocean floor.

Subduction Zone

a long, narrow zone where one tectonic plate is forced beneath another, typically an oceanic plate descending beneath a continental plate or another oceanic plate. This process recycles oceanic crust into the mantle and often results in deep ocean trenches, earthquakes, and volcanic activity.