First we talked about the surface of the Earth and the children drew the continents on a balloon. Aiden showed me a circle on the bottom of his balloon and said, "Look Mommy, I drew Antarctica!" Ahhh..proud homeschool mommy moment.
We made yummy models of the Earth using peanut butter (MANTLE), chocolate shell (CRUST) and Red Hots (CORE). First, I gave the children a blog of peanut butter on wax paper along with a few Red Hots.
and asked them to place the Red Hots in the center and rolled the peanut butter around it into a ball. Then we placed our Earth's in the freezer for an hour. When we took them out the children added the chocolate shell. Once it hardened they sliced their Earth's in half named each part and ate them!
We talked about things that can change the Earth's crust like earthquakes, erosion and volcanoes. we made a shake table by placing the top of a boot box upside down in a tray on top of marbles. There is a wonderfully challenging experiment sheet I used with the older children: lego experiment activity sheet . The younger ones had fun making their buildings!
The used water, ice and wind (blew through a straw) to see how they shaped the Earth through erosion. They used an experiment sheet and each formed a hypothesis as to which would cause erosion the quickest.
Aiden is four so volcanoes never get old:)
The children used crayon shavings to model how sedimentary and metamorphic are formed. They wrapped a pile of shavings in aluminum and then placed it under a large dictionary and took turns sitting on it to model sedimentary rock being formed by pressure. Then after they made their observations I held a lighter under it to model how metamorphic rocks are formed.You can find more detailed instructions at the Flying Fox Academy blog.
This one was soooo much fun. The little boys mixed up a batch of 'rock' clay. Then they placed it on aluminum foil and put pieces of a plastic dinosaur skeleton we found at the Dollar Store on each 'rock, wrapped them up and I baked them. Check out Homemade Mamas for the recipe and instructions.
They looked and felt just like rocks when we pulled them out of the oven! The children opened up their 'rocks' and put all the fossils together to form a dinosaur! Super fun!
Then we made our own fossils. I put acorns, shells, leaves, etc. on the table and gave each child a ball of crayola clay on wax paper to use to make their impressions.
The children brought their rock collections to co-op. We used a Venn diagram and the children came up with different rules to sort the rocks. They sorted using attributes like color, texture, size, etc. Then they moved to the exploration table. They observed, weighed, measured, and tested for buoyancy at this table. The older ones used gram weights and the little ones used plastic teddy bears to weigh their rocks. I left this up all week for Elle and Aiden to revisit. 
