Introduction to Earth Science Chapter 1

Essential Questions 1.What does an Earth Scientist study? 2.What information do various maps give to an Earth Scientist? 3.How do Earth Scientists (and all scientists) seek knowledge?

Overview of Earth Science Earth science is the name of the group of sciences that deals with Earth and its neighbors in space. Earth science is divided into four broad categories:

The Earth Sciences Geology—the study of the solid Earth Oceanography—the study of the Earth’s oceans Meteorology—the study of the Earth’s atmosphere Astronomy—the study of the Earth’s place in the universe

Formation of Earth The Nebular Hypothesis suggests that bodies in our solar system evolved from an enormous rotating cloud called the solar nebula. Mostly hydrogen and helium, with some heavier elements.

Differentiation As the newly formed Earth cooled layers formed through a process called differentiation. Denser elements (iron and nickel) sink to the Earth’s core. Lighter rocks and materials migrate outward forming the mantle and crust.

A View of the Earth Earth can be thought of as consisting of four major spheres: Hydrosphere Atmosphere Geosphere Biosphere

Earth’s Major Spheres The hydrosphere includes all liquid water on Earth—both saltwater and fresh water. The atmosphere consists of the gaseous envelope surrounding the Earth. Although the atmosphere extends more than 100km up, 90% is within 16km of the surface.

Earth’s Major Spheres The biosphere includes all life on Earth. The biosphere is concentrated in a zone that extends from the ocean floor upward several kilometers in the atmosphere. The geosphere consists of the solid parts of the planet and is not uniform. Based on differences in composition it is divided into three main regions, the core, the mantle, and the crust.

Geosphere Divisions The dense core has two parts; a solid inner core and a liquid outer core. The rocky mantle is divided into an lower mantle and upper mantle. The rock in the upper part of the upper mantle is somewhat flexible and pliable—it’s called the asthenosphere (weak sphere).

Geosphere Divisions The outer crust is divided into continental crust and oceanic crust. This rigid outermost layer is called the lithosphere (rock sphere).

Plate Tectonics The lithoshpere is broken into several sections called plates. The Theory of Plate Tectonics states that earthquakes, volcanoes, mountain building, and the movement of continents are the result of the movement of lithospheric plates.

Earth System Science Earth system science aims to study the Earth as a system made up of numerous interacting parts, or subsystems. A system can be any size group of interacting parts that form a complex whole.

Earth as a System The Earth system is powered by two sources of energy: The Sun– which drives external processes in the atmosphere, hydrosphere, and at the surface. The Earth’s interior heat—which drives plate tectonics.

Each system affects the other. The actions of nature and people produce changes in all of the other parts of the Earth system. Resources (some renewable, some not), population, pollution, global warming, species extinction, etc. are some examples.

Scientific Inquiry All science is based on two big assumptions: 1.The universe behaves in a consistent and predictable manner. 2.Through study, we can understand this behavior.

Hypothesis Once observations have been made and data gathered, scientists try to explain how or why things happen in the manner observed. They state a possible explanation called a scientific hypothesis.

Theory Once further observations have been made and/or tests performed, scientists either accept, modify, or reject their hypothesis. The hypothesis is elevated to a Scientific Theory once it has been well tested and accepted by the scientific community as the best explanation of observable facts.

Representing Earth’s Surface MAPPING Specifying a location on Earth’s surface is done using a grid system of latitude and longitude. Latitude is the distance north or south of the equator (measured in degrees). Longitude is the distance east or west of the prime meridian (also in degrees).

The Global Grid

Because lines of latitude never meet they are also known as… Parallels: circles around the globe N or S of the Equator Each degree consists of 60 equal parts called minutes. Each minute is divided into 60 equal parts called seconds.

Because lines of longitude never meet they are also known as… Meridians: semicircles running from pole to pole. As with latitude, there are minutes and seconds:

Great Circle: any circle that cuts the Earth into a perfect half. any 2 lines of longitude directly across from each other on opposite sides of the globe, or the Equator (the only parallel of latitude that forms a great circle)

Great Circle: any circle that cuts the Earth into a perfect half.

Using Coordinates Both latitude and longitude are needed to locate positions on Earth precisely. When giving coordinates, latitude is always given first.

Latitude: 38° 8' 57" N 38 degrees, 8 minutes, 57 seconds North Longitude: 79° 4' 18" W 79 degrees, 4 minutes, 18 seconds West

Distance 1.The distance on Earth's surface for each one degree of latitude or longitude = 69 miles (111 kilometers) 2.The distance between lines of latitude remains constant. Why? 3.What happens to the distance between lines of longitude as you move north or south of the Equator?

Time Zones Earth is divided into 24 time zones Why 24?

Earth takes about 24 hours to rotate once on its axis (360°) 360° ÷ 24 hours = 15° per hour Each time zone is 15° wide Each time zone represents a different hour

International Date Line (IDL) 180° meridian gain or lose a day travel WEST across the IDL ► advance one calendar day (add 24 hours) travel EAST across the IDL ► move back one calendar day (subtract 24 hours)

Why is the IDL crooked?

Wed. Feb. 2, :05:50 Tues. Feb. 1, :05:50 Why is the IDL crooked?

Maps and Mapping No matter what type of map is made, some portion of the surface will always appear too small, big, or out of place. Cartographers (mapmakers) have found ways to limit the distortion of shape, size, distance, and direction.

Types of Maps Maps are flat projections that come in many different forms

Reading a Map Legend: list of symbols and their meanings Scale: ratio between distances on a map and actual distances on Earth’s surface 1:25,000 - one unit on the map equals 25,000 units on Earth’s surface

Map Projections Map projection: a flat map that represents a 3-dimensional globe

The Mercator Projection 1.Accurate at the equator and highly distorted at the poles. 2.Directions accurate 3.Size and distance distorted.

Robinson Projection Shows most distances, sizes, and shapes accurately. Distortions present along edges.

Other map projections: A conic projection is made by wrapping a cone around the Earth at a particular line of latitude. (almost no distortion at that line) A gnomonic projection is made by placing a sheet of paper on a globe so that it is touching only one spot. See page 13 in text.

Topographic Maps Topographic maps show Earth’s elevation using contour lines. All spots along a particular contour line have the same elevation.

Topographic Maps The contour interval on a topo map gives the user the difference in elevation between each contour line. Geologic Maps are those that also contain information about the type and age of rock formations in the area.

More on maps All maps represent a certain area so a scale is included to compare actual distances. Satellites have made accurate cartography much simpler than in the past.