Conglomerate: what do its round pebbles tell us?
1 min 37 s. The words are spoken and shown in the picture; the player can also show them as subtitles.
For the Earth and Space Sciences Regents. Topic: Sedimentary rocks, with the past questions on it.
What Dr. Mars says (the words of the video)
Conglomerate: what do its round pebbles tell us?
Dr. Mars holds a handful of angular pebbles.
Angular means they have sharp corners.
He drops them into a fast stream.
Fast water has the energy to carry pebbles.
The pebbles knock against each other and the stream bed.
Their sharp corners are rubbed away, so they become rounded.
The farther they travel, the rounder they become.
Where the stream slows, the pebbles settle.
The energy of the water decides the size of the grains.
More sediment buries them. Its weight packs them closer together.
Minerals from the water cement the pebbles together.
Now they form a rock called conglomerate.
Find compaction and cementation on the Rock Cycle Infographic in the Reference Tables.
Dr. Mars breaks a pebble out of a conglomerate cliff.
It is rounded, like the pebbles in the stream.
Rounded pebbles mean moving water carried them a long way.
Check yourself! Which water can carry pebbles: A, B, or C?
Think about the energy of the water.
Answer: A! Fast water in a stream can carry pebbles.
Like the stream where Dr. Mars dropped his pebbles.
Dr. Mars. Free practice for the New York Earth and Space Sciences Regents.