INTRO TO MARINE SCIENCE - Chapter 1

Reading Notes

1.        How and when did the universe form?

The universe formed roughly 13.8 billion years ago during an event known as the Big Bang during which a cataclysmic explosion caused the universe to rapidly increase in size

1.        How and when did our solar system form?

About 5 billion years ago, a single, rotating, interstellar cloud of gas and dust exploded. As it collapsed, the speed of rotation increased and flattened, forming a disk with our sun at the center. The molecules of dust and gas began to collide and stick together, causing the planets to form.

1.        What processes added heat to the early Earth, and how was Earth’s interior changed by the heat?

Earth was bombarded by particles of all sizes, and a portion of their energy was converted into heat on impact. As the heat was trapped, it raised the temperature of the Earth’s interior. When the interior reached the melting point of iron and nickel, the melted elements migrated toward the center of the planet, and the less dense material moved upward and spread over the surface, cooling and solidifying.

1.        What were the sources of the early Earth’s oceans and atmosphere?

Gases released from Earth’s hot, chemically active interior formed the first atmosphere which was primarily made up of water vapor, hydrogen gas, hydrogen chloride, carbon monoxide, carbon dioxide, and nitrogen.

1.        How old is Earth?

Between 4.5 and 4.6 billion years old

1.        How and why have estimates of the age of Earth changed over the past few hundred years? Do you think the present estimate of Earth’s age will change in the future?

The estimated age of the Earth has changed because people calculate the age using different processes such as rate of addition of salt to the oceans from rivers or dating rocks using radioactive decay. I think the estimate of Earth’s age might change a little bit as we get more technology that can be more precise with dating rocks or even coming up with new techniques for dating.

1.        How are rocks dated?

Rocks are dated using a process known as radiometric dating using radioactive isotopes and their half-lives which can give us an idea of how long a rock has been on Earth.

1.        How much of a radioactive isotope would be left after two half-lives have passed?

1 quarter of a radioactive isotope will be left after two half-lives have passed.

1.        How were the divisions of geologic time established before age-dating of rocks was possible?

Geologic time was established by using the appearance or disappearance of fossil types.

1.        Why are the Arctic and Antarctic Circles located at 66 ½ degrees north and 66 ½ degrees South?

They are located because during the solstices, the sun does not rise above 66 ½ degrees North, nor does it set south of 66 ½ degrees

1.        What is the shape of Earth

Earth is nearly spherical with a slight bulge at the equator.

1.        Why isn’t Earth a perfect sphere?

Earth isn’t a perfect sphere because as it spins, it tends to flatten at the poles and bulge along the equator

1.        Relate Earth’s highest elevations and greatest depths to its overall size.

Earth’s highest elevations and greatest depths are minor/unnoticeable compared to Earth’s overall size

1.        Why is the equator a unique parallel, whereas the prime meridian is an arbitrary choice?

The equator is the only line of latitude that is also a great circle, and the prime meridian was established by an international agreement to create a universal reference for longitude and time zones

1.        Why are the Arctic and Antarctic Circles displaced from the pole by 23 ½?

They are displaced 23.5 degrees due to Earth’s axial tilt of approximately 23.5 degrees relative to its orbital plane.

1.        How is time important in the calculation of longitude?

Earth’s rotation causes 15 degrees of longitude to correspond to one hour of time

1.        Will we always be able to use the North Star to determine latitude? Why?

No, while the North Star is currently aligned with the Earth’s rotational axis, the alignment is temporary, and over thousands of years, other stars will become the North Star

1.        What is the relationship between the hydrologic cycle and climate zones?

The properties of climate zones are principally determined by their surface temps and their evaporation-precipitation patterns controlled by the hydrologic cycle

1.        What percentages of Earth’s surface are covered by water and by land?

71% of land is below sea level, 29% is above sea level

1.        How does the distribution of seawater and land differ in the Northern and Southern Hemisphere?

In the Northern Hemisphere, most of the land lies in the middle latitudes, and the Southern Hemisphere has land located mostly in the tropical latitudes and in the polar region.

1.        What does the hypsographic curve reveal about the differences in elevation and depth of continents and the ocean floor?

It reveals that 20% of all land areas are at elevations above 2 km and 85% of the ocean floor is deeper than 2 km.

1.        Name the five ocean basins in order of their area from larger to smallest.

Pacific, Atlantic, Indian, Southern, Arctic

Radiometric Dating

measures the proportion of radioactive isotopes and their decay products; relies on decay rates of the isotopes to calculate the time elapsed since the material formed or crystallized

Summer Solstice

• June 22 is the day with the longest period of daylight and the beginning of summer in the Northern Hemisphere

• On this day, the sun does not sink below the horizon above the Arctic Circle, nor does it ride above the Antarctic Circle

Autumnal Equinox

• September 23 is when the sun stands directly above the equator; on this day the periods of daylight and darkness are equal all over the world

Winter Solstice

• December 21 is when the daylight period is the shortest in the Northern Hemisphere; above the Arctic circle, the sun does not rise, south of the Antarctic circle, the sun does not set

Vernal Equinox

• March 21 the sun stand above the equator and spring begins in the Northern Hemisphere; the periods of daylight and darkness are equal around the world

• Between the Tropics of Cancer and Capricorn, there is little seasonal change in solar radiation because the sun is always nearly directly overhead at midday hours

Sideral Day

• about 4 minutes shorter than the mean solar day; it gives the true rotational period of earth and is useful in astronomy and navigation

Great Circle

defines the shortest distance connecting any two points on Earth’s surface

Reservoirs

places in which water resides

Hydrologic Cycle

water is constantly moving into and out of reservoirs

Transpiration

the release of water by plants

Sublimation

the conservation of ice directly to water vapor

Residence time

the average length of time that a water molecule spends in any one reservoir

Hypsographic Curve

graph of depth or elevation versus Earth’s area