Name: ____________________________________________________ Date: _______________ Block: _____ DBQ #1 - Earth's Grid System Read the following passage and answer the questions that follow. Long before astronauts traveled into space, people had to guess about Earth's shape. Some thought it was flat. Others thought it was a disc. However, no one had real proof about its shape. That is until ancient Greek geographers came along. They were some of the first scientists to figure out the shape of our planet. These geographers used mathematics and their observations to design the first globes. These globes were our first models of Earth. Earth has a geographical grid. It is important to learn about this grid so that you can understand globes. This grid is found on flat maps and on globes. It is a pattern of horizontal and vertical lines. These lines intersect at coordinates. Geographers use these coordinates to locate places on Earth, on maps, and on globes. The vertical lines are called lines of longitude or meridians. Lines of latitude or parallels are the horizontal lines. Hipparchus was a Greek geographer. He was born in 150 B.C. Hipparchus divided Earth into 360 sections. These sections are called degrees. These sections were drawn on the globe to show lines of longitude. Meridians run from pole to pole and divide the Earth vertically. In 1884, scientists created our prime meridian. It measures 0 degrees (0º) longitude and runs through Greenwich, England. If you sail up the Thames River to Greenwich, you will find the Royal Naval Observatory. This is where you will see a marker for the prime meridian. Distance is measured east or west of the prime meridian. As you travel east, the meridians measure 1º to 179º. This is also the eastern hemisphere. Travel west from the prime meridian and you will enter the western hemisphere. The meridians in this hemisphere measure from 1º to 179º. You are probably wondering about the 180th degree. Well, it's there! You can reach it by traveling from the prime meridian either east or west. This meridian is halfway around our planet from the prime meridian. The 180º meridian is also called the International Date Line. Parallels separate Earth into horizontal hemisphere. The equator is the starting line for latitude. Like the prime meridian it measures 0º. In Africa and South America you will find markers to show where the equator is located. As you move north from the equator, you enter the northern hemisphere. Parallels are numbered from 1º to 90º as you move north or south of the equator. The southern hemisphere is the area from the equator to the South Pole. Knowing about latitude and longitude is the easy part. Now we need to talk about their measurements. Degrees are used when measuring parallels and meridians. There are 360º in a circle. That is why the Earth and globes are separated into 360 one degree sections. Earth is a three-dimensional circle or sphere. Minutes are smaller units within degrees. You have learned there are sixty minutes (60') in an hour. In latitude or longitude there are also 60 minutes between each degree. Geographers also divided the minutes into seconds. Remember our clock? Well, there are 60 seconds in each minute. This is also true for each minute of latitude and longitude. If you were to look at a globe, you would only see the degrees for the meridians and parallels. What about the lines in-between? You would have to imagine these lines. There are nine one-degree marks between each parallel and meridian. Latitude lines are used to separate climate zones. If you were to study a world map or globe, you would see these climate zones. They are the temperate and tropic zones. In the northern hemisphere the temperate zone runs from the Arctic Circle to 23º 30' north latitude. The Arctic Circle is 66º 30' north latitude. The area from 23º 30' north latitude to the equator is the Tropic of Cancer. The Tropic of Capricorn is found in the southern hemisphere. It runs from the equator to 23º 30' south latitude. The southern temperate zone runs from 23º 30' south latitude to the Antarctic Circle. Speaking of the ends of the Earth, let's talk about our poles. When you imagine the North and South Poles, you think of very cold places. In addition to their ice, there is a more important reason to know about these poles -- magnetism. All lines of longitude meet at the northern and southern-most points. These are our poles. However, there are two types of north poles. They are the geographic north pole and the magnetic north pole. Geographic North Pole is where the Earth's longitude lines meet. It is exactly 90º north of the equator. Another name for this region is true north. The magnetic north pole is close to true north. Remember your globe? Well, true north is the pole that runs through the globe. Magnetic north is based on the Earth's magnetic attraction. The Earth is really a huge magnet. This magnetism comes from its center. To find magnetic north on Earth, you need a compass. Compass needles on Earth always point to magnetic north. Why? The needle on a compass is magnetized. This means that it was rubbed with a magnet. Since it is made of metal, it becomes attracted to the Earth's magnetic field. No matter what direction you are facing, a compass needle always points to magnetic north. The Earth's geographic grid is a valuable measurement tool. It helps geographers and other people to locate places on Earth. Following these lines you will learn more about locations on our planet. Answer the following questions based on the reading passage above. 1. How is the magnetic North Pole different from the geographic North Pole? 2. What is the area called from the equator to the North Pole? 3. Each degree of latitude or longitude is divided into ______. a. 60 minutes c. 66 minutes b. 60 seconds d. 66 seconds 4. Climate zones are separated by ______. a. The South Pole c. Latitude lines b. Longitude lines d. The North Pole 5. Why do you think scientists developed the prime meridian in 1884? 6. If the Arctic Circle measures at 66º 30' north latitude, what is the measurement for the Antarctic Circle? 7. Meridians measure from ________ east or west from the prime meridian. a. 1º to 169º c. 1º to 180º b. 1º to 179º d. 1º to 170º 8. Parallels are numbered from 1º to 89º north or south of the equator. a. True b. False .