If you haven't already stumbled across Fossils, Facts & Finds they have a great range of free resources (and more available to purchase). Here you can find the Clock of Eras chart and links to explanations for each era, as well as some other handy reference materials.
Layers of the Earth
The Helpful Garden is always a good starting place for free materials, check out their Layers of the Earth cards.
Montessori Mom also has a simple set of cards for The Layers of the Earth.
For the older child these cards from Cultivating Dharma are a great find
The Pinay Homeschooler also has a free set of materials for the Layers of the Earth.
Land and Water Forms
Land and Water Forms cards with definitions can be found within this Earth Unit post by Every Star Is Different. They also share their play dough Layers of the Earth experience.
Land and Water Form Cards from The Helpful Garden
Advanced Landforms from Montessori Mom
Imaginary Island studies bring together several geography concepts in one activity.
Parts of a Volcano from Montessori Mom
Parts of the Volcano nomenclature cards from The Helpful Garden
Active Volcanoes (picture cards) from The Pinay Homeschooler
Rocks and Minerals
The Little School House in the Suburbs has a great set of Rocks and Minerals classified cards.
Free Igneous and Metamorphic Rocks printable's from The Pinay Homeschooler.
Rock Cycle chart - This is an excerpt from some resources I am developing at the moment.
Tectonic Plates and Earth Quakes
Earthquake cards from Montessori Mom
I will be sure to keep adding to this list as I find more resources.
Here are some affordable materials that you may like to consider as well - all of which I have used and suggest with no affiliation (other than my own materials):
Parts of a River from Montessori Print Shop
Parts of a Mountain from Montessori for Everyone
Parts of the Volcano including definition cards from The Learning Ark
Igneous, Sedimentary & Metamorphic Rocks from Montessori Print Shop
Land and Water Form cards with definition cards at my TpT store
Advanced Land and Water Form cards with definitions available at my TpT store
For more resources, activities and extensions be sure to take a look at my dedicated Pinterest board
Follow Elementary's board Geology Roundup on Pinterest.