Have you ever noticed how some rocks appear to have layers? You just may be looking at sedimentary rock! Each of these are formed in different ways with different characteristics that make them unique!
In this experiment we’ll explore how sedimentary rock layers contribute to its formation!
What is Sedimentary Rock?
Sedimentary rocks often have flat layers and are composed of pieces that are roughly the same size with pores between filled with smaller grains. Interestingly, sedimentary rocks sometimes contain fossils.
What are the Three Types of Rock?
Three classes of rock exist, igneous, sedimentary, and metamorphic.
Igneous
A huge hint as to how igneous rock forms is the fact that it comes from the word ‘ignis’ meaning ‘fire.’ Igneous rock is formed when molten rock, such as magma from the Earth’s core or lava from a volcano, cools. Igneous rock has a crystalline structure, meaning they’re made of interlocking crystals. When igneous rock is made quickly (cools slowly) you’ll get large crystals, but if it’s cooled quickly, you’ll get either microscopic or no crystals (forming glass!).
Sedimentary
Sedimentary rocks form when small pieces of the Earth that have been worn away by wind and water accumulate at the bottom of rivers, lakes and oceans and are eventually compacted and consolidated into rock. They can also be formed when sea water evaporates, and the dissolved minerals are deposited on the sea floor.
Metamorphic
Metamorphic rock forms deep within the Earth where there is high heat, high pressure and hot mineral-rich fluids. These conditions interact with igneous, sedimentary rock and cause it to change into a new structure (without melting). This is called metamorphism and changes the rock into a new structure. Interestingly, older metamorphic rock can continue to change into new types of metamorphic rock through this same process.
Materials
- Glass jar with lid
- Water
- Rocks
- Pebbles
- Sand
- Soil
How to Create Sedimentary Rock
Step 1
Go on an adventure with a parent or guardian to collect your rocks, pebbles, sand, and soil from around your home and/or neighbourhood.
Step 2
Fill a jar about ⅓ full of your rocks, pebbles, sand and soil. Then, fill the rest of the jar with water.
Step 3
Make a prediction! What do you think will happen if the jar is shaken? Will the jar completely mix?
Gently shake the jar.
STEM Q for You: What happened to each of the materials within the jar?
Each settled into layers!
Step 4
Take a measurement of each of the sizes of the layers and order them largest to smallest.
STEM Q for You: Where are each of the layers located?
From largest to smallest they are most likely ordered rocks, pebbles, soil, sand.
Step 5
Try re-shaking the jar and watch the materials resettle.
STEM Q for You: Do the materials resettle in the same place each time?
Yes!
Next time: Try adding other layers into the mix, such as mud or other rocks. Where do they layer within the tower?
Why Did the Materials Settle in that Order?
Materials settled into layers according to their weight, with the coarser, heavier material at the bottom and the finer, lighter layers on top.
Where Do Sedimentary Rocks Form?
Sedimentary layers usually form in lake beds and near running water such as swamps, lakes, seas, and oceans. After a long period of time, they will turn into rock.
