Layers of the Earth: A Classroom Activity

Photo by NASA

Photo by NASA

From the core to the crust, the Earth is a pretty big deal. It has a diameter of about 6,400 km, and it is made of various layers that help change the surface of the earth. These layers are defined by either what they are made of or how they move. When we look at the chemical composition of each layer, we are defining them as compositional layers. The compositional layers are the crust, the mantle and the core. When we look at the mechanical properties of the layers, we are defining them as the mechanical layers. The five mechanical layers are the lithosphere, the asthenosphere, the mesosphere, the inner core and the outer core. Although we only see the outermost layer of the earth, we have learned a lot about the layers underneath by looking at seismic waves and various rocks at the surface. 

The three compositional layers of the earth are defined by significant changes in chemical composition. The outermost layer is the crust. It is the thinnest layer making up only about 1 percent of the earth. The crust is mostly made of elements like silicon (Si), aluminum (Al), potassium (K), calcium (Ca), oxygen (O), sodium (Na) and minerals made of these elements. The crust can be subdivided into two types – oceanic crust and continental crust. Oceanic crust tends to be thinner (approx. 5-10km thick) than continental crust and younger too! Continental crust is on average 30 km thick, and contains the oldest rocks and minerals. Both types of crust cover the entire outer portion of the earth. Below the crust lies the mantle (approximately 2,890 km thick.) The mantle is made of silicon (Si) and oxygen (O) like the crust, but it also contains large amounts of iron (Fe) and magnesium (Mg). The final compositional layer of the earth is the core (approx.3,480 km thick). The core is made of iron (Fe) and nickel (Ni). It is under intense pressure and high temperatures, and it is the densest layer of the earth. Although these layers may share common elements, the contents differ enough to create the distinct layers.

The five mechanical layers of the earth are defined by how the layers move. The layers can be described as rigid, plastic or liquid in consistency. The outermost mechanical layer is the lithosphere. The lithosphere is rigid, and it includes the crust and the uppermost part of the mantle. The lithosphere is divided into the tectonic plates, areas of continental crust and/or oceanic crust that move and shift over time. The tectonic plates of the lithosphere move and shift on the plastic layer called the asthenosphere. The asthenosphere is under more pressure than the lithosphere and has a higher temperature. It is considered plastic because the rock has the ability to flow more than a rigid layer, but not as easily as a liquid layer.  The rock in the asthenosphere could melt if exposed to the surface, but it is under extreme pressure causing it to flow like a plastic. The mesosphere is the layer below the asthenosphere. The mesosphere is hotter than the asthenosphere, but it is rigid because it is experiencing more pressure than the layers above. The last mechanical layers of the earth are found in the core. The core is split into the outer core and the inner core because the two layers differ in rigidity. The outer core is liquid iron (Fe) and nickel (Ni). The flow of the outer core creates and sustains the earth’s magnetic field. Unlike the outer core, the inner core is solid. The inner core is made from mostly iron (Fe), but it can also contain nickel (Ni) and traces of precious elements like gold (Au). It is extremely hot, and under extreme pressure from the layers of the earth and atmosphere around it. All of these layers work together to make our dynamic earth!

Create a foldable Earth with the activity below to teach students about the various layers of the earth. To learn how the asthenosphere moves tectonic plates or learn about the natural disasters caused by that movement, check out our new Earth Science on Wheels topic Dynamic Earth!

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This project models two different ways to understand the layers of the earth. It addresses the compositional layers of the earth, and the mechanical layers of the earth.

Materials:

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Procedure:

  1. Pass out template to each student.
  2. Instruct students to cut out the Earth. Once they have cut the outside, tell them to cut along the dashed line that says “cut here.”
  3. Next, fold along the “Fold line.” Then, set the Earth aside.
  4. Now, tell students to cut out the quarter circle labeled A. This will represent the mechanical layers of the earth.
  5. Invite students to color each of the areas in the quarter circle a different color starting from the inside:
    1. Yellow – inner corre
    2. Orange – outer core
    3. Red – mesosphere
    4. Pink – asthenosphere
    5. Purple – lithospherecut and colored edit
  6. Have students set aside the mechanical layers (A.) for now
  7. Instruct students to cut out the second quarter circle (B.) from the template sheet. These will represent the compositional layers of the earth. Invite students to color each of the sections a different color:
    1. Yellow – core
    2. Red – mantle
    3. Brown – crust
  8. Have students set aside the compositional layers (B.) for now
  9. Instruct students to glue the earth, to the background paper. Remind them to not glue down the flap.
  10. Tell students to place the mechanical layers (A.) on the background paper underneath the flap and glue it to the paper.
  11. They should then take the quarter circle that represents the compositional layers (B.), and place it on the backside of the flap of the Earth. Then, carefully glue it to the back of the flap.
  12. Once completed, show students how to flip up the flap and see the mechanical layers on the background page and the compositional layers on the back of the flap. Students can add notes to the layers to help them learn what the layers do!
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A Practical Application of the Fundamentals of Physics.

 

Gravity, the force that attracts a body toward the center of the Earth, seems to be out to get me. I have been described as being “made out of fall down”. This is because I fall down. A lot. I have long legs and big feet and sometimes I don’t pick them up, so I trip. I ride my bike to work a lot and sometimes the potholes get me. Occasionally my adventures in science result in mystery bruises. Bruises and scrapes I can handle, but recently I had the opportunity to test some of Newton’s Laws in other ways.

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I, in my little Dodge Caliber, was hit by a GMC pickup truck. After I took a hot minute to get my wits about me, I crawled out and looked at was left of the tail end of my car. My first thought? “Good job, crumple zones. Good job….” This is how we got to this blog entry. It’s been a while since High School Physics, so let’s all get caught up on some basics:

  • Inertia is the tendency of an object to resist any change in its velocity (speed+direction).
  • A fancier way to say that? Newton’s First Law of Motion states that a body at rest remains at rest unless acted upon by an external force and a body in motion continues to move at a constant speed in a straight line unless it is acted upon by an external force.
  • Force = Mass x Acceleration (if Acceleration is the rate of change of the velocity)

 

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In other words, unless some outside force acts on an object it will keep on going or staying, as the case may be. One of those outside forces is friction. Which brings us to inertia. A bigger, heavier object will take longer to get to a high rate of speed, but if the same force is applied, it will also take a longer time to slow down too. So a ping pong ball takes a lot less effort to stop than a freight train, but it also takes a lot less effort to throw a ping pong ball than it does a freight train. And so that brings us to the practical application portion of today’s blog.

Specifically, in the case of my accident, my little car had almost come to a stop when I was hit from behind. Since the truck was so much bigger, the truck had more momentum than my car brakes could handle—so I was pushed forward, even though the truck slowed significantly.

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Even though there was a lot of damage done to the rear end of my car, I was still safe. This is because some physicists and engineers (thank you!) have been working to make vehicles safer. To do this, they have to take into account Newton’s Laws of Motion. Some of the safety features cars have these days are seat belts, crumple zones, air bags and specialized tires. Since you can’t instantaneously change the mass of the vehicles in an accident, your best bet is to change the acceleration to reduce the force. The function of the seat belts, crumple zones and air bags is to do just that by slowing things down more gradually. They change the acceleration of the person inside the vehicle by increasing the time it takes for the accident to occur – even if it is just by fractions of seconds.

Seatbelts comprise about 50% of your protection in a car. When a driver stops the car suddenly, the driver tends to lunge forward, because the driver’s body tends to maintain its speed and direction. The seat belt holds the driver and prevents the driver from flying forwards when the car stops. Seat belts help by applying a force that overcomes your inertia as in Newton’s First Law. They also increase the time in the wreck which results in a lesser impact force on you; more time means less acceleration to you! Even when your body comes to a stop, however, your internal organs continue to move, slamming against each other because of the impact. So, that’s fun.

Good tires are also an important safety feature on your car. The friction between the tires and the road determines the maximum acceleration and the minimum stopping distance. If the surface of a tire is rougher, then the friction force is larger. This is super important if you are slamming on your brakes to avoid something or speeding up, also to avoid something.

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Prior to 1959, people believed the more rigid the structure, the safer the car. This ended up being deadly because the force from the impact went straight to the passenger. Crumple zones are specially engineered areas on your car that are designed to absorb energy as they are crushed and slow down the rest of the car more gradually. They absorb energy from a collision and therefore reduce the force of a collision on the passengers. They aren’t just spots that are softer or less dense on the car, they are specifically engineered to crush in a relatively gradual and predictable way that absorbs much of the impact energy, keeping it away from the occupants in what is termed a “controlled crush”.

So! Buckle up and be safe, and good job, crumple zones…good job.

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Sports Science: Olympics Edition ‒ Javelin

Every four years, the eyes of the world shift towards a global competition, complete with feats of strength, determination, talent and teamwork. The Summer Olympics are back, and I could not be more excited. The following post is one of three about some of my favorite events.

This go-around, I’m rather excited to further study one event in particular. After the 2012 London Olympics, I returned to St. Louis for my junior year of college to find that my roommate decided to join the Washington University track and field team. Why? “I just wanted to be better at throwing spears.”

As he soon learned, Javelin is much more complicated than just throwing a spear. The best javelin throwers have spent decades perfecting their technique. And when I tried to just pick up a javelin and throw it for fun, the result was too embarrassing to share here.

First, there’s the run-up, the series of steps where the thrower is building up speed and momentum. This begins with a traditional run and transitions into crossover steps before the actual throw. The crossover steps are when a thrower swivels his shoulders and hips and orients his body to prepare to release without sacrificing velocity. As a result of the run-up, some athletes can throw the javelin at speeds up to 30 meters per second, or about 100 kilometers per hour!

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As the thrower prepares for the delivery, there has to be a transfer of energy from the body to the javelin itself. This process is started by planting the back foot while still keeping the throwing arm as straight as possible. The front foot continues the transfer by stopping and planting in as straight and rigid a manner as possible. This abrupt stop will force the body to swing around as momentum continues to carry it forward. The athlete must control this swing yet remain rigid in the front foot as much as possible to generate the most force.

Once the front foot plants, a chain reaction of sorts proceeds up the body, transferring force and energy from the legs to the javelin through a series of joints. The back knee swivels forward, followed by the back hip, moving upwards to the shoulder, out to the elbow and finally the javelin.

The javelin is released over the shoulder at an angle ideally between 32 and 36 degrees, according to Mike Barber’s excellent post on the biomechanics of the javelin. As Barber astutely points out, the more important angle measurement is the difference between the angle at which the javelin’s point is moving and the angle at which the javelin’s center of gravity is moving. Ideally, the difference is zero and the pair align to produce the maximum distance. A variation in those angles means the javelin will not travel in the most aerodynamic way possible and, due to increased drag, will not go as far.

Javelin throw at Gay Games 9 Cleveland + Akron

Keep your eye on the motion of the body right at the moment of release of the top javelin throwers. Their arms are straight throughout the run up, and the muscles in their legs have to be strong and robust to handle the abrupt stop required for the best throws. There is a lot of stress put onto their bodies as a result, and they must be in top physical shape.

The javelin throw finals at the Rio Olympics will take place on Aug. 18 for women and Aug. 20 for men.

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HMNS Happenings This Week

Mark Your Calendars for these events happening at HMNS August 15 – August 21

Poppe-shell

NEW EXHIBIT OPENING!

Gems of the Sea: The Guido T. Poppe Collection
Opens August 19, 2016

World class. One of a kind. Never before seen. Made by mollusks.

The Philippines consists of over 7,500 islands in Southeast Asia, totaling a land area of approximately 116,000 square miles, and giving the Philippines the longest coastlines of any nation in the world. The Philippine archipelago is known to possess some of the richest marine biodiversity in the world. Along with their unparalleled diversity among the species, marine mollusks from this area are of great interest to science for their peculiar interactions and adaptations in their marine environment.

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Behind-the-Scenes Tour:

Planetarium – Black Holes
Tuesday, August 16, 6 p.m.

Explore the history, physics and mystery of black holes, and explores several of the latest scientific theories about how black holes are formed and where they are hiding now. Witness the bending of light, the skewing of perception, and the dizzying descent into a black hole.

Embark on a journey through one of the most mystifying, awe-inspiring phenomena in the universe with Dr. Carolyn Sumners, HMNS VP of Astronomy, for a special evening viewing of Black Holes in the newly upgraded Tru 8K Burke Baker Planetarium. Click here to learn more.

LECTURE:

Gems of the Sea – Deep Water Shells
Thursday, August 18, 6:30 p.m.

HMNS malacologist Tina Petway will relate how ecology and science benefit from research-quality shell collections. This special evening celebrating the addition of the Poppe Collection to HMNS’ shell collections will include a preview of the Gems of the Sea exhibition as well as tours of select portions of the Cullen Hall of Gems and Minerals, Strake Hall of Malacology and Morian Hall of Paleontology. Click here to learn more.

Erin Mills Cockrell Butterfly Center

 

Last Week of Summer CBC Events 
Wing It | Tuesday at 10:30 a.m.
Watch the release of hundreds of new butterflies into the rain forest.

Small Talk | Wednesday at 11 a.m.
Join our Cockrell Butterfly Center team as they take their live collection of insects out “for a walk” during Small Talk.

Friday Feeding Frenzy | 9:30 a.m., 10:30 a.m. & 11:30 a.m.
See science in action as snakes, spiders and centipedes enjoy a meal right in front of you!

 

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