Transcript 4/20 & 4/21 - 7th Grade Agenda

2/18 & 2/19 - 7th Grade Agenda
Learning Objective: Learn about Index Fossils
Collect HW: Conducting Scientific
Investigation Worksheet
Collect HW: Signed Grade Printout
Video: Walking with prehistoric beasts
Text Book Reading: 270 – 277
HW: Reading & Notetaking p. 135 – 138
Reminder Science Fair Board due 2/25 &
2/26(50 Points)
Reflection
• Prompt: Describe how Igneous,
Sedimentary and Metamorphic rocks are
created.
What is relative age of a rock?
• The relative age of a rock is its age
compared to the ages of other rocks
What is the absolute age of a
rock?
• The absolute age of a rock is the number
years since the rock was created.
Which layer is the oldest layer of
rock?
• Bottom Layer is the
Oldest Layer
• Law of superposition: In
horizontal sedimentary
rock layer the oldest layer
is at the bottom. Each
higher layer is younger
than the layers below it.
What is Igneous Intrusion?
• Igneous Intrusion
forms when magma
cools and hardens
beneath the surface
• Igneous intrusion is
always younger than
the rock layer around
and beneath it.
Which is older? The fault or the
rock layer?
• A fault is a break in
earth’s crust.
• A fault is always
younger than the rock
it cuts through.
Why is there gaps in the
Geologic Record?
Unconformity is a
gap in the
geologic record.
What is an index fossil?
• Index fossils help geologists match rock
layer
• To be useful as an index fossil, a fossil
must be widely distributed and represent a
type of organism that existed only briefly.
Which fossils are index fossils ?
Trilobite
Ammonite
These rocks are some of the
oldest fossils in the world. How
old are they?
• Stromatolites:
Remains of ocean
reefs created by
bacteria more than 3
billion years ago.
What is Radioactive Decay?
• Radioactive Decay:
over time, unstable
elements break down
or decay by releasing
particles and energy.
What is half-life?
• The half-life of a radioactive element is the
time it takes for half of the radioactive atoms
to decay.