McKnight's Physical Geography 11e Lectures Chapter 1 Introduction to Earth Andrew Mercer Mississippi State University © 2014 Pearson Education, Inc.

Learning Goals of This Chapter Distinguish the key concerns for geographers who study the world. Analyze how geographers use science to explain and understand the natural environment. Identify the four environmental “spheres” of Earth. Illustrate how the concept of Earth systems helps us to understand the interrelationships of the four environmental “spheres” of Earth. Describe Earth’s relationships within the solar system. Compare the size of Earth with the size of its surface features.

Learning Goals of This Chapter Determine the latitude of a location on Earth. Determine the longitude of a location on Earth. Locate a place given the latitude and longitude coordinates. Explain how latitude and longitude together identify a location on Earth. Summarize the factors that cause the annual change of seasons. Describe the changes in the patterns of sunlight around Earth during the year. Explain how time zones were established.

Learning Goals of This Chapter Describe how time zones are used to establish actual times around the world. Discuss the relationship between time zones and the international dateline.

Introduction to Earth Geography and Science Environmental Spheres and Earth Systems Earth and the Solar System The Geographic Grid – Latitude and Longitude Earth–Sun Relations and the Seasons Telling Time

Geography and Science “GEO”-”GRAPHY” Adjective to denote sub-field Location & Distribution Physical/Human

Establishment of scientific theory Geography and Science The scientific method Observe phenomena Formulate a hypothesis Design an experiment to test the hypothesis Predict the outcome of the experiment Conduct the experiment Draw conclusions Scientific “proof” Establishment of scientific theory

Geography and Science Measurement systems Need measurement systems to quantify scientific processes SI versus English units Conversions

Geography and Science Unit conversions

The Environmental Spheres Four primary spheres Lithosphere – “stone” Atmosphere – “air” Hydrosphere – “water” Biosphere – “life” 2 3 1 4 Interactions between the spheres

The Environmental Spheres Earth systems Closed systems – those contained from outside influence Open systems – energy and matter free to be exchanged across systems Equilibrium – systems are in balance (input = output) Interconnected systems – change in one system affects another (example of a glacier) Feedback loops, positive versus negative

The Environmental Spheres Positive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A. In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback

Earth and the Solar System Earth’s physical characteristics Maximum relief See figure Imperfect sphere Equatorial diameter ~ 12,756 km Polar diameter ~ 12,714 km Circumference of 40,000 km

The Geographic Grid – Latitude and Longitude Location on Earth Need an accurate location on Earth to describe geographic features Use Earth’s rotation axis to base location on the surface North Pole and South Pole Plane of the equator

The Geographic Grid – Latitude and Longitude Great circles Circles that bisect a sphere and pass through the sphere’s center Identify the shortest distance between two points on a sphere—great circle distance Plane of the equator is a great circle Small circles

The Geographic Grid – Latitude and Longitude Graticule Latitudes Angle north or south of the equator Parallels Seven important latitudes Latitude zones

Seven important latitudes

Latitude zones

Latitude zones If you can't pinpoint which of the four zones you live in, simply google "latitude of the name of your city." Once you have the latitude of your city, you'll know which of the four zones you live in: Tropics: 0 to 23 degrees (eg. Honolulu, HI: 21 degrees) Subtropics: 23 to 35 degrees (eg. Atlanta, GA: 33 degrees) Mid-Latitudes: 35 to 50 degrees (eg. Chicago, IL: 41 degrees) High Latitudes: 50 to 70 degrees (eg. Anchorage, AK: 61 degrees)

The Geographic Grid – Latitude and Longitude Longitudes Angular description of east–west direction Meridians Important longitudes Convergence at poles Location on the graticule based on latitude and longitude

Important longitude lines

International Date Line

Grid system

Earth–Sun Relations and the Seasons Rotation of the Earth 24 hours for one rotation Circular motion at all latitudes but the poles Rotation is counter-clockwise relative to the North Pole Converge at the poles Diurnal transition from light to darkness (circle of illumination) Tidal effects from the Moon and Sun Coriolis force

Earth–Sun Relations and the Seasons Earth’s revolution around Sun One revolution takes 365 ¼ days Elliptical orbit Aphelion (152,100,000 km) Perihelion (147,100,000 km) Average distance (149,597,871 km)

Earth–Sun Relations and the Seasons Orbital Properties Plane of the ecliptic Earth’s axis tilted at 23.5° relative to ecliptic Polarity of the Earth’s axis Parallelism North Pole always points toward Polaris (“North Star”) Combined effects contribute to seasons

Earth–Sun Relations and the Seasons Two important conditions Angle of the sun above the horizon Length of day – circle of illumination Two solstices June solstice December solstice Two equinoxes March equinox September equinox

Earth–Sun Relations and the Seasons

Earth-Sun Relations

Earth–Sun Relations and the Seasons June solstice Occurs on approximately June 22 each year Sun directly overhead at 23.5° N latitude Antarctic Circle in 24 hours of darkness, Arctic Circle in 24 hours of daylight Marks start of summer in Northern Hemisphere; winter in Southern Hemisphere

Earth–Sun Relations and the Seasons December solstice Occurs on approximately December 22 each year Sun directly overhead at 23.5° S latitude Arctic Circle in 24 hours of darkness, Antarctic Circle in 24 hours of daylight Marks start of winter in Northern Hemisphere; summer in Southern Hemisphere

Earth–Sun Relations and the Seasons Equinoxes Occur on approximately March 20 and September 22 each year Day length 12 hours worldwide (“equinox”) Sun directly overhead at the equator Latitude receiving vertical rays Varies between the Tropic of Cancer (June solstice) and Tropic of Capricorn (December solstice)

Earth–Sun Relations and the Seasons Day length Longest in Northern Hemisphere on June solstice Opposite in Southern Hemisphere Arctic and Antarctic day length variations

June 21

March 20 & Sept 22

Dec 21

Earth–Sun Relations and the Seasons Significance of seasonal patterns Spread of solar rays over small and large areas Tropical latitudes consistently warmer Polar latitudes consistently cooler Large seasonal variations in temperature in midlatitudes

Telling Time Current time system 24 time zones Greenwich Mean Time (GMT) (also known as Universal Time Coordinated [UTC]) is standard Controlling meridian for each time zone Several countries have multiple time zones in their borders Time zone boundaries subject to local, political, and economic boundaries of different nations 180° meridian the International Date Line a.m. and p.m. ???

Telling Time Time zones of the world

This arch that stretches over an autopista indicates the Prime Meridian in Spain.

Telling Time Time zones of the United States

Daylight-savings time Telling Time Daylight-savings time Move clocks ahead by an hour during the summer months Originally done by Germans during WWII; now practiced by many nations Conserves lighting energy by providing an extra hour of daylight

Daylight Saving Time

Summary Geography is the study of the distribution of physical and cultural attributes of Earth. Many sciences have branched off of geography. The scientific method is important when doing scientific studies. Earth has four primary spheres, the atmosphere, the lithosphere, the hydrosphere, and the atmosphere.

Summary The solar system formed 5 billion years ago and consists of eight planets. Earth is an imperfect sphere. A latitude and longitude grid helps identify locations on Earth’s surface. Earth rotates on its axis in 24 hours. Earth revolves around the Sun in 365 ¼ days. Tilt of Earth’s axis causes seasons.

Summary Equinoxes and solstices help identify when a seasonal transition occurs. Time zones were established to have a uniform global time system. Daylight-savings time was devised to conserve energy by adding an hour of daylight.