The document discusses four geologic principles - uniformitarianism, superposition, original horizontality, and catastrophism - and compares each principle to the layers of a cake. Uniformitarianism is like a cake in that the ingredients and process of making a cake are always the same. Superposition is like a cake as the bottom layer was placed first and each subsequent layer above it is younger. Original horizontality is like cake layers in that they should be placed horizontally. Catastrophism is like a dropped cake that is suddenly ruined. The document provides additional examples comparing the principles to other everyday items like clothes piles and bicycles.

1. Evocative Question
How are the
geologic
principles for
understanding
the Earth’s
history like a layer
cake?

2. Uniformitarianism
 The geologic processes that happen today
(mountain building, volcanoes, rocks)
happened the same way in the past AND
change on the Earth is occurring slowly and
constantly.
 How is this like a cake?
 The Principle of Uniformitarianism is like a layer
cake because people basically make cakes the
same way every time.

3. Superposition
 In horizontal sedimentary rock layers, the
oldest layer is at the bottom. Each higher layer
is younger than the layers below it.
 How is this like a layer cake?
 The Principle of Superposition is like a layer cake
because the bottom layer was put down first
(oldest) and the top layer was placed last
(youngest).

4. Original Horizontality
 Sediment settles out of water in
horizontal layers. Larger sediment
settles first and smaller sediment
settles later. Sedimentary rocks form
in horizontal layers.
 How is this like a layer cake?
 The Principle of Original Horizontality is like a
layer cake because the layers should be placed
horizontally.

5. Catastrophism
 Geologic Change occurs suddenly
 How is this like a layer cake?
 The Principle of Catastrophism is like a layer cake
because if you drop it, it’s gone wrong suddenly!
http://www.flickr.com/photos/sylvia/5727154433/sizes/m/in/photostream/http://www.flickr.com/photos/sanfranannie/3639238588/sizes/m/in/photostream/

6. More Simile Examples
 Before you get ready to write your own
similes, here are a few more examples that
are not related to cake.
 The Principle of Superposition is like your dirty
clothes pile. The shirt you wore longest ago is
on the bottom, and the shirt your wore most
recently is on the top.
 The Principle of Uniformitarianism is like riding
a bike. You always ride a bike in the same
way.
 The principle of Original Horizontality is like a
house. The floors in a house are laid out
horizontally.

7. More Simile Examples
 Before you get ready to write your own
similes, here are a few more examples that
are not related to cake.
 The Principle of Superposition is like your dirty
clothes pile. The shirt you wore longest ago is
on the bottom, and the shirt your wore most
recently is on the top.
 The Principle of Uniformitarianism is like riding
a bike. You always ride a bike in the same
way.
 The principle of Original Horizontality is like a
house. The floors in a house are laid out
horizontally.