We use the ETC Montessori Clock of Eras, which is a little bit different than most of the printable, free, or low-cost options that are available. Instead of a 12 hour clock, they have the equivalent of a 24 hour clock by giving the Archean Eon it's own 12 hour period. I like this because it emphasizes just how long geological history was in the formation periods.
What We Teach
As Catholics, we teach that science and religion can only complement each other. In 1988, Pope John Paul II noted, "Science can purify religion from error and superstition; religion can purify science from idolatry and false absolutes. Each can draw the other into a wider world, a world in which both can flourish."
In super simple terms, this means that science can tell us a lot about how we think things happened but it can never tell us why it matters or why it happened. Case in point, when I first introduced the Archean Eon, Aidan piped up that this is like in the Bible before creation began and God was alone in a formless world. I have yet to come across a situation when the kids were confused by surface conflicts between faith and science. There are fundamental flaws in both literal creationism and strict darwinism. I'm not going to debate this in the comments or otherwise, this is just what we believe. Read more about Catholicism and science here and here.
When We Teach It
I deviate from traditional Montessori approach to the Great Lessons and history. We use a rotational approach to history which means I tend to cover the Great Lessons on an as-relevant basis instead of each year as designed. The same goes for the Clock of Eras and Timeline of Life. I teach the same base lessons to all of the kids and modify follow-up work as necessary for ability.
This year is the first in our rotation and, as we are back to ancient history, we are starting the year with the Clock of Eras. From the Clock of Eras we will move into the Timeline of Life, covering history and science/geography together up to that point. At the end of the Timeline of Life study, we will branch off with history study jumping to Ancient Egypt and returning to biomes for science/geography and more in-depth species study. Throughout, I will intersperse some of the Great Lessons as they relate to other areas of study. For example, we will definitely do the Story of Signs and Symbols (Writing) this year.
How We Teach It
Presentation 1: Overview of The Clock
In the first presentation I provide an overview of what the clock is, brief descriptions of each era/eon noted, and show straight line strips emphasizing the long period of black (this is usually done separately in an earlier lesson). This is the most impressionistic of the lessons I give, mostly aiming to give a big picture understanding of the vast enormity of time. As follow up work, all I ask is that each child spend a period of time working with the manipulative parts of the clock.
Additional Presentations: Individual Era/Eons
After the initial overview of the clock, I present each era individually, beginning with Archean. I use the blank booklets available for free download on Everything Fossils. There is tons of great information, including some information on the Clock of Eras and for each era (right sidebar). If you click on the Clock of Eras link you will find the booklets we use, there is also additional information under Montessori Materials. For each presentation I include the relevant geography charts to help tell the story of the era. Then I give each older student a blank booklet and ask them to illustrate it and have younger students do a one page drawing of what they remember of the era (so in the end they will have one booklet instead of several).
Final Presentation: Bridge to Timeline of Life
During the Paleozoic, Mesozoic, and Cenozoic Eras changes to life of earth were happening very quickly. We could never look at the changes on a timeline that included all of geological time so we have to look at them separately. My album includes a separate timeline with a long black strip and then a stretchy elastic end to show how we stretch out that section of the clock into the timeline. I find a regular piece of elastic works just as well. I cut it (not stretched) to the arc length of those periods on the clock and then stretch it to show how much more we can fit. The timeline is the elastic stretched out.
If you have any questions about the Clock of Eras, leave a comment and I will do my best to answer!
This post has been linked to Montessori Monday at Living Montessori Now.