Introduction To The Earth

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SWBAT state the shape of the Earth and provide (3) pieces of evidence for its spherical shape SWBAT identify the three (3) major zones of the Earth and analyze the structure and composition of each layer

Big Idea

Students analyze pieces of rationale for why the Earth is round, and they'll also get an introductory glimpse into the major zones of the Earth

Lesson Introduction

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 2.1 - Introduction To The Earth (Whole Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 2.1 - Introduction To The Earth (Whole Lesson). Finally, students need their Earth Science Reference Tables [ESRT] (particularly Page 1) for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

This lesson is the introductory component of the Dynamic Earth unit, which covers the interior of the Earth, earthquakes, tectonic plates and continental drift, and a few other processes and principles. This lesson is aligned to address the concept that the Earth is actually not a perfect sphere, but is an oblate spheroid, a shape caused by the bulging at the Equator due to its dynamic rotation. Additionally, we explore the pieces of evidence that "prove" the Earth has this nearly spherical shape. Finally, we utilize the Earth Science Reference Tables (ESRT) to analyze the composition of varying Earth layers. 

Do Now & Objective(s)

10 minutes

Students come in silently and complete the Do Now. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions, although this one can be done in about two minutes), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material;
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

The Shape of the Earth and Evidence for Earth's Shape

15 minutes

In this section, I introduce the pieces of evidence that effectively "prove" the shape of the Earth.

The first part starts with Fun Fail Motorcycle Merry-Go-Round video, which shows a practical, and humorous demonstration of inertia. 

I show this video as an introductory piece to explain Earth's shape as an oblate spheroid. The man on the merry-go-round ultimately is thrown off by the rotating force of the merry-go-round. In effect, when the Earth is rotating, it's doing the same thing. Gravity is holding it together, but the equatorial region at the center is being distorted due to its rotation. This same force also causes a "flattening" at the poles, which is what gives Earth its actual shape - an oblate spheroid.

Wo continue the lesson by having students explore the image on the bottom of the first page of the resource here: Evidence for Earth's Shape. This image gives actual quantitative numbers that show the polar and equatorial diameter. You can refer to the embedded comments,  but I usually ask a series of basic checks for understanding ("What do you notice about the difference in the equatorial and polar diameters?"), and then ask them to explore in partners where the force of gravity would be both the greatest and the least. [The force of gravity would be greatest at the poles, as the polar diameter is marginally less than the equatorial diameter, which means the poles are closer to the center of gravity]. 

I then ask them to think about some pieces of evidence that we can claim show the Earth's shape. There is an image in the document showing one method - that ships sink lower on the horizon as they sail away from shore due to the curved surface of the Earth. There's also the fact that astronauts have visually confirmed the shape from space, and that gravity is reasonably (although, from the work above, we know that it isn't exact) uniform across Earth's surface at sea level. As always, please reference attached comments (download the Word document in the 'Lesson Introduction' section for any additional context and information). 

Parts of the Earth

10 minutes

In the Parts of the Earth section, we introduce parts of the Earth: the atmosphere, hydrosphere, and lithosphere (crust). The attached chart from the first page of the Earth Science Reference Tables [ESRT] shows the elemental composition by volume (and mass, for the crust) of key elements that make up each of these layers. A key component here, and what will form one of the underlying and unifying themes of the course, is the notion of density. The layers themselves are arranged via their density (crust/lithosphere, hydrosphere, and the atmosphere, respectively), and students get their first glimpse into seeing that density provides a sort of natural order in terms of arranging and layering particles. They will see this many more times throughout the course (and there is a density specific unit which can be accessed here), but this is a key concept to reinforce for students. 

I usually have them analyze the chart by providing some basic checks for understanding (i.e. - "What two elements make up more than 60% of the Earth's crust by mass?" [Silicon and Oxygen]), but they're also going to be doing some application to this during the upcoming Regents-aligned practice session, so it's helpful to not get to bogged down in this section. 


15 minutes

The lesson itself is fairly information dense, so it's important to prioritize Practice for students to "cement" a lot of this information from the lesson. All of the questions were pulled from a Regents-aligned test bank that I use, and I like to give them uninterrupted space to try out the application of all of this stuff in an authentic way. In a lesson like this, given the above-mentioned information density, I try to prioritize checking in with some of my students who are struggling a bit more. I also try to have students periodically refer back to their notes or reference tables if they have questions, or are struggling with a problem. 

I included a list of multiple-choice and free response questions, and we usually have the chance to review and go over the questions, pending enough free time. I always allot some time to review questions of particular importance, (#s 8, 9, and 10 being the most critical here, due to their inherent difficulty and the "need" to go over them to fully encapsulate student understanding) or that hit on key concepts in the lesson that are vital to student understanding. 

Exit Ticket & Closing

10 minutes

Depending on the amount of time left, I have students complete the exit ticket. It is graded communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson. We then usually wrap up, I give students time to pack up their belongings, and I usually end the class at the objective (which is posted on the whiteboard, in addition to being on their 'Do Now' at the start of each lesson) and ask students two questions:

  1. Do you feel that you mastered the objective for the day?
  2. Can you reiterate one thing you learned about ____________ (in this case, the shape of the Earth, or evidence for its shape, etc.)

See the attached reflection in this section for some additional rationale behind why I end the class this way.