Download Grade Seven - Science - Miami

2nd Nine Weeks Topics
MIAMI-DADE COUNTY PUBLIC SCHOOLS
Parent Resources
7 Grade Science Topic Highlights
Questions to ask your child
Layers of Earth
November
VI. Layers of Earth
A. Crust and Lithosphere
B. Mantle
C. Core
D. Comparing Layers of
the Earth
Question to learner: The geosphere is all of the rocks and minerals of Earth. How are the
layers of the geosphere structured?
Sample Response: The three main layers of Earth are the crust, mantle, and core. These
layers vary greatly in size, composition, temperature and pressure (force pressing on an
area). The temperature and pressure inside Earth increases with depth. The crust is the
outer layer made of solid rock that includes both dry land and the ocean floor. Earth’s mantle
is made of rock that is very hot, but solid. The crust and uppermost mantle are grouped into
a single layer called the lithosphere. The core is made mostly of the metals iron and nickel. It
consists of two parts—a liquid outer core and a solid inner core. The outer core is a layer of
molten metal surrounding the inner core. The inner core is a dense ball of solid metal. The
movements in the liquid outer core create Earth’s magnetic field.
Plate Tectonics
November - December
VII.
Plate Tectonics
A. Continental Drift
B. Describing Tectonic
Plate Movement
C. Explaining Plate
D. Movement through
Heat Flow
Question to learner: How do moving plates change Earth’s Surface? What makes this a
theory?
Sample Response: Earth’s tectonic plates are in slow, constant motion, driven by convection
currents (cyclical movement that transfers heat) of material in the mantle. Earth’s plates
move because they are on top of the large convection currents in Earth’s mantle and may
move towards, away from or alongside neighboring plates resulting in different features on
Earth's surface. Earth’s plates can carry ocean floor, continents, or continents and oceans
together. The convergence, or coming together, of plates can create mountains, volcanoes,
and deep ocean trenches. During subduction (the sinking of plates into the interior of Earth),
gravity pulls denser plate edges downward, into the mantle. The spreading apart,
divergence, or plates can lead to ridges. Transform boundaries are the most common cause
of earthquakes as the tension build from plates sliding alongside each other is released.
Plate tectonics is a theory because it is supported by a vast body of evidence that is used to
explain many observations (such as earthquakes, volcanic eruptions, and mountain
building).
Division of Academics – Department of Science
November-January Topic Highlights
Page 1 of 1
MIAMI-DADE COUNTY PUBLIC SCHOOLS
Parent Resources
7 Grade Science Topic Highlights
Rock Cycle and Processes that Shape Earth’s Surface
December
VIII. Rock Cycle and Processes
that Shape Earth’s Surface
A. Rock Cycle
B. Review of Landforms
and Apply to Florida
C. How Humans Impact
the Earth
Question to learner: How are different landforms shaped by the rock cycle?
Sample Response: The rock cycle involves many processes that shape the surface of the
Earth include physical and chemical weathering (the breaking of rock), erosion (the
movement of rocks and smaller sediments), and deposition (the laying down of sediment).
These processes in the rock cycle are responsible for landforms such as coastlines, runes,
rivers, deltas and lakes and are primarily comprised of sediments and sedimentary rocks.
Plate tectonics is also responsible for processes that transforms rocks within the geosphere.
By forcing some rocks into the interior of the earth, some rocks become hot enough to melt
into magma. When this magma cools, the result is an igneous rock. Other rocks do not
reach a high enough temperature to melt, but under great pressure are transformed into
metamorphic rocks. As the pressure from plate tectonics pushes rocks up to the surface of
the Earth, mountains are built.
Age of Earth/Geological Time
January
IX. Age of Earth/ Geological
Time
A. Measuring the Age of
the Earth
B. Evidence of Changes
to Earth
Division of Academics – Department of Science
November-January Topic Highlights
Question to learner: How do scientists study Earth’s past?
Sample Response: The Earth has evolved over geologic time (many millions of years) due to
natural processes. Current methods for measuring the age of Earth and parts of the Earth
include the Law of Superposition and radioactive dating. According to the law of
superposition, the deeper a rock layer, the older it must be. Each higher layer is younger
than the layers below it since rock layers and build by new sediment adding to the lower
layers. You can imagine this as similar to a laundry hamper, where the clothes that were
worn longest ago end up at the bottom at the hamper, while more recently used clothes are
at the top. These layers of rocks (or clothes) maybe be shifted around to not stay in perfectly
straight layers. Earthquakes can cause fault lines that break and shift rock layers and other
movements of rocks can cause layers to fold around each other. This method doesn't
provide an exact or numerical age. Instead the law of superposition is used to determine
relative ages of a group of rocks such as "younger" or older". Radioactive dating uses a
chemical analysis of rocks to determine an approximate numerical age.
Page 1 of 2