Ref. Table Warm-Up (pg. 10) What is the actual temperature range of the outer core? Approx. 5,000 C – 6,200 C

Ref. Table Warm-Up (pg. 10) At a depth of 2000 km what is the approximate temperature of the mantle? Approx. 4,200 C

In this unit we will measure Earth several different ways Mapping the Earth In this unit we will measure Earth several different ways First we will look at earth's shape Is it’s shape spherical or not spherical?

A. The earth is nearly spherical. Evidence: 1. Ship masts appear 1st on horizon when the ship is sailing towards you.

Ships appear to sink gradually below horizon when sailing away

The 2nd and most important proof that Earth is round is the fact that the altitude of Polaris increases as you move toward the North pole, or decreases as you move toward the equator! This is the star that lies in space practically over the geographic North Pole of the earth.

Polaris changes in altitude depending where you are – Polaris is a fixed point above the North Pole. 90º

Polaris If you stood at the North Pole, Polaris would be almost directly overhead.

Why do observations of Polaris help determine the Earth’s shape????? The North Star appears lower and lower in the sky as you travel toward the equator because of earth’s spherical shape, where the North Star is just visible at the horizon. The latitude of the equator is 0°.

The most important thing to remember… ALTITUDE OF POLARIS = LATITUDE OF OBSERVER

Locating Polaris – our latitude is 43°N , Polaris’ altitude will be 43°

Question What is the altitude (angle) of Polaris in the sky from a person at 15 degrees N latitude? 15 degrees

Actual Regents Question At which location will the highest altitude of the star Polaris be observed? A) Equator B) Arctic Circle C) central United States D) South America

LUNAR ECLIPSE!!! Only a sphere can cast a shadow that appears round. During a lunar eclipse, the earth casts its round shadow on the moon

The last form of evidence…

Pictures from space IT’S ROUND!

Summary: How did they prove the Earth to be round? Not on Notes! Ships appear to sink GRADUALLY below the horizon as they travel away from observer Polaris (North Star) changes altitude (angle measured in degrees above earth’s surface) directly with your latitude ALT OF POLARIS = LAT OF OBSERVER Lunar Eclipses - Earth’s shadow on the moon Satellite Imagery – absolute proof

EARTH’S SHAPE B. Earth is NOT a perfect sphere, however. It is an oblate spheroid. NOT THIS EITHER – BUT CLOSE! NOT THIS! This shape is called an oblate spheroid NOT THIS! Earth looks more like this!

It’s not really as “oblate” or oval as I drew it on the previous slide Oblate Sphere Not on Notes It’s not really as “oblate” or oval as I drew it on the previous slide

Which of these is closest to Earth’s actual shape? REGENTS QUESTION! Which of these is closest to Earth’s actual shape? 2. 3. 1.

1. The weight of an object depends on the distance from the earth’s center. An object’s weight is less the further it is from earth’s center

Where on Earth would this pumpkin weigh the most? Why?

At the Poles we are closer to the center = stronger gravity = more weight Center of Earth= center of gravity

The exact same pumpkin (object) would weigh slightly more at the poles than at the equator

What causes Earth to bulge at the equator? Answer:EARTH’S ROTATION

Earth’s Rotation Why does the Earth bulge at the equator? Warm-Up Review Why does the Earth bulge at the equator? Earth’s Rotation

Warm-Up Review If Santa was standing at the north pole at what angle would he have to look to see Polaris? 90 degrees (straight up)

The circumference of the Earth is closest to… Warm-Up Review The circumference of the Earth is closest to… 20,000 km 2) 30,000 km 3) 40,000 km 4) 50,000 km

Where would the pumpkin weigh the most? Warm-up Review Where would the pumpkin weigh the most? Sea level at the Equator Sea level at the poles or

Inner Core Ref. Table Question 6,500 degrees C Pretend you are at a depth of 6,000 km inside the Earth. What layer would you be in, and what is the actual temperature? 6,500 degrees C Inner Core

Ref. Table Question (pg.14) What is the temperature at 50 km above seal level 0 degrees C

Ref. Table Question (pg.14) What is the water vapor concentration in the mesosphere? 0 g/m3

MEASURING EARTH C. Earth’s circumference - distance around the earth. 1. 1st measured by Eratosthenes 2000 years ago. a. Measured distance between Egyptian cities Alexandria and Syene. b. Measured sun’s angle at noon at each location.

c. Difference in angle is a fraction of a circle. d. Multiply distance by fraction to get circumference. e. Obtained 46,250 km, very close to the real 40,000 km circumference!

Eratosthenes Method If I told you that the green section is 6 feet around the outside, could you tell me the circumference of the whole pie? Talk with your partner!

Solutions to the Problem! A complete circle contains 360 degrees, half of which is 180 degrees. SO if half of the pie has a circumference of 6 feet what must the other half have? 6 Feet also! Pg. 19 of your textbook

Now here’s what Eratosthenes actually did He observed the sun on June 21, in Alexandria and Syene – 2 cities in Egypt. On this date, the sun was straight overhead at noon in Syene, but not quite overhead at Alexandria

Syene Alexandria 7 degree difference

Using simple geometry he set up an equation that determined the circumference of the earth.

360 degrees / 7.2 degrees = 50 Proportions JUST LIKE THIS EXAMPLE

Eratosthenes knew if he could figure out any portion of the 360 circumference of the Earth he could solve for the whole circumference! He was very, very close for not having technology. He determined the circumference to be about 46,000 km.

The actual circumference is… Back to Note Packet EARTH’S DIMENSIONS The actual circumference is… Equator- 40,074 km Poles- 40,007 km.

Regents question You will be using Eratosthenes' method to find the circumference of planet X. At noon, when a vertical stick at the Equator casts no shadow, a vertical stick 1,000 kilometers away casts a shadow and makes an angle of 60 degrees

What is the CIRCUMFERENCE? 1,000 km. 60 degrees What is the CIRCUMFERENCE?

1,000 km. 6,000 km.

E. Lithosphere The lithosphere is the outer solid part of the earth, including the crust and uppermost mantle

What is the Hydrosphere? The hydrosphere includes all the water on Earth

THE ATMOSPHERE The atmosphere is the layer of gas that surrounds Earth above the surface of liquid water and rocky material

Troposphere Stratosphere Mesosphere Thermosphere The zones of the atmosphere are the Troposphere Stratosphere Mesosphere Thermosphere Each has its own distinct characteristics such as temp. and composition

In meteorology we will focus more on the layers of the atmosphere

The earth is 29% lithosphere and 71% hydrosphere More land or water on Earth’s surface? The earth is 29% lithosphere and 71% hydrosphere

C. Earth’s density = 5.5 g/cm3 TOPIC II- DENSITY A. The amount of material in a given space Density = mass volume B. Units = g/cm3 C. Earth’s density = 5.5 g/cm3

DENSITY BROKE MY HEART

What is the density of this rock? The rock has a mass of 10 grams It has a volume of 5 cm3 Density = M/V Answer = 2 g/cm3

A) 42 g/cm3 B) 0.20 g/cm3 C) 28 g/cm3 D) 5.0 g/cm3 What is the density of a rock which has a mass of 35 grams and a volume of 7.0 cubic centimeters? A) 42 g/cm3 B) 0.20 g/cm3 C) 28 g/cm3 D) 5.0 g/cm3

The density of the Earth as a whole is 5.5

It is the boundary between the crust and the mantle Moho Discontinuity It is the boundary between the crust and the mantle

The crust is thickest under the mountains, thinnest under oceanic crust

Deepest hole ever drilled was around 6 km The Moho is about 8km beneath the oceanic crust, and 32 km beneath the continents Operation Mole Hole Deepest hole ever drilled was around 6 km

H. Temperature below the surface

1. At 20 m, the temperature remains the same all year round. 2. As you go deeper than 20 m, the temperature rises 1C with each 40 m increase in depth. 3. Earth’s core = 7000C Hot!!!

Any evidence of a heat source existing below the surface?

I. Source of Earth’s Heat: Mostly radioactive elements Friction between rocks in Earth’s crust 3. Leftover original heat from earth’s interior

THE END

Rough Vs. Smooth: Its all relative! When standing on Earth looking at the Grand Canyon the Earth’s surface looks very rough. This is because you are comparing the surface with your self as a frame of reference (a scale to compare size) When seen from space the Earth looks very smooth. This is because you are comparing the mountains and valleys with the entire planet for scale!

Perspective and Frame of Reference…what its all about! Comparing a canyon that is 1.6 km deep with your height of .002 km makes it seem very large! Comparing that same canyon with its depth of 1.6km, with the average diameter of the planet 12,756 km makes it seem very small. Mount Everest is approximately 8.850km, compared with 12,756 it seems pretty small. For this reason scientists say that the Earth is SMOOTH relative to its dimensions.

Proportions! A proportion is making the mathematical statement that two ratios are equal Eratosthenes knew if he could figure out any portion of the 360 circumference of the Earth he could solve for the whole circumference! Remarkably, Eratosthenes determined the circumference to be 25,000 miles, just 99 miles over the actual circumference at the equator (24,901 miles) What was his percent error? %D = . 398%!!!!!

EARTH’S SPHERES The three spheres are lithosphere, hydrosphere, and atmosphere in order of decreasing density! The lithosphere and atmosphere are divided up into separate spheres as well!

Notice that altitude here means height above sea level, and not the altitude of Polaris! Notice that pressure decreases with altitude, and so does water vapor. In fact, there is no water vapor above the troposphere. Temperature does not have such a predictable trend. The temperature changes are caused by the different gases that make up the layers. The gases are arranged by density.

Where are we? How would you keep track of where you are on such a big planet? At first, people used stars…

USING STARS TO NAVIGATE Early sailors used a device like this to know where they were on this huge Earth The device was used to measure the angle between a star, and the horizon. This angle is the altitude of the star.

The Altitude of Polaris By far the most important star was Polaris, or the North star, because the altitude of Polaris told you how far North of the equator you were (latitude!) Remember as distance increases the altitude decreases or angular distance from the horizon! But how to find Polaris? Contrary to popular belief Polaris is NOT the brightest star in the northern hemisphere sky, in fact it barely makes the top 50!!

Finding Polaris! Much more important then Finding Nemo! Polaris is also called the North Star, or the Load Star. Just look for the Big Dipper -- and notice that the Dipper has a bowl and a handle. Draw a line between the two outermost stars in the bowl of the Big Dipper. This line points to Polaris, the North Star!

Additionally: Most stars rise and set -- just like the sun and moon Additionally: Most stars rise and set -- just like the sun and moon! But Polaris is like the hub of a wheel -- it stays put in the northern sky, while all the other stars appear to circle around it (in fact we are spinning on our axis and Polaris is centered above our axis!)

Latitude is: The Angular distance north or south of the equator Parallel lines, equator is zero degrees, north pole is 90 degrees north EQUAL TO ALTITUDE OF POLARIS!!!

LONGITUDE AND TIME Since longitude is determined by taking the time of solar noon (sun at maximum altitude in the sky for the day) at your location and comparing it to solar noon at the prime meridian. It is known that the Earth makes one complete rotation about its axis every 24 hours. 360 degrees divided by 24hrs calculates to 15 degrees/hr.

Greenwich Time! If you know time at one location, you can say that it is one hour earlier for every 15 degrees to the west. Another way : The occurrence of any time moves west at 15 degrees per hour. So when you measure your solar noon if it is 2:00 PM in Greenwich (on prime meridian) you know you are 30 degrees west of Greenwich!

LONGITUDE IS…. Angular distance east or west of the prime meridian Longitude lines are not parallel, and get closer together as you move towards the poles NOT determined by the location of Polaris, but another star – THE SUN!

Longitude lines run up and down (North & South) and determine your location east or west of the prime meridian Latitude lines run east/west and determine your location north, or south of the equator