Cambridge & Gifted 6th &7th Grade Science
INTRO TO CLASSIFYING LIFE
What are the questions we will explore in this section of our BIOLOGY UNIT?
How can we tell if a thing is alive, dead or has never been a living thing?
Let's look at some examples and try to sort them as as alive, dead or non-living (has never been a living thing)
A Jurassic ammonite?
A 3D headset?
Is there a criteria we can use to make this decision?
Can looking at processes like movement, breathing or respiration, excretion, growth, sensitivity and reproduction help us to identify living and non-living things?
Viruses cannot reproduce the way most things we identify as living things do - but they do reproduce very successfully so it time for scientists to look again at whether or not viruses can be considered living things?
Among living things how do we define what a species of living things are?
What are some tools we could use to classify living things into population groups?
In the discussion page please send me 3 questions you have about this unit and one thing you think will be interesting to learn about.
What is inheritance? Working in teams complete section A of this GIZMO
For Period 2
This is the Kahoot link
LAYERS OF THE EARTH
How do we know the Earth’s interior structure is like this model? (We don’t)
#1- Tracking the waves produced by earthquakes.
#2- The force and materials from volcanoes.
#3- The property of density.
#4- The magnetic field around the Earth.
#5- Rock samples from Earth’s past.
Scientists use evidence to create models that put together a theory of how things work and they change it as new evidence is discovered.
The solid crust is the outermost and thinnest layer of our planet, it makes up 1% of the volume of Earth. The crust averages 25 miles (40 kilometers) in thickness and is divided in to 15 major tectonic plates that have geologic activity at the boundaries, such as earthquakes and volcanism.
The most abundant elements in the Earth’s crust include oxygen, silicon, aluminum, iron, and calcium. These elements combine to form the most abundant minerals in the Earth’s crust, members of the silicate family – plagioclase and alkali feldspars, quartz, pyroxenes, amphiboles, micas, and clay minerals.
All three rock types (igneous, sedimentary, and metamorphic) can be found in Earth’s crust. Crustal material is classified as oceanic crust or continental crust.
Oceanic crust underlies our ocean basins, is thin, approximately 4 miles (7 kilometers) in thickness, and is composed of dense rocks, primarily the igneous rock basalt.
Continental crust is thicker, ranging from 6 to 47 miles (10 to 75 kilometers), and has a high abundance of the less dense igneous rock granite.
The oldest rocks on our planet are part of the continental crust and date back approximately 4 billion years in age.
Ocean crust is constantly recycled through our planet’s system of plate tectonics and only dates back to approximately 200 million years ago.
The mantle makes up 84% of the volume of Earth. As Earth began to take shape about 4.5 billion years ago, iron and nickel quickly separated from other rocks and minerals to form the core of the new planet. The molten material that surrounded the core was the early mantle.
Over millions of years, the mantle cooled. Water trapped inside minerals erupted with lava, a process called “outgassing.” As more water was outgassed, the mantle solidified.
The rocks that make up Earth’s mantle are mostly silicates and magnesium oxide.
The temperature of the mantle varies greatly, from 1000° Celsius (1832° Fahrenheit) near its boundary with the crust, to 3700° Celsius (6692° Fahrenheit) near its boundary with the core. In the mantle, heat and pressure generally increase with depth.
The viscosity of the mantle also varies greatly. It is mostly solid rock, but less viscous at tectonic plate boundaries and mantle plumes. Mantle rocks there are soft and able to move plastically (over the course of millions of years) at great depth and pressure.
THE UPPERMOST LAYER OF THE MANTLE & THE CRUST are the LITHOSPHERE
The mantle’s outermost zone is relatively cool and rigid. It behaves more like the crust above it. Together, this uppermost part of the mantle layer and the crust are known as the lithosphere.
The most well-known feature associated with Earth’s lithosphere is tectonic activity. Tectonic activity describes the interaction of the huge slabs of lithosphere called tectonic plates.
The asthenosphere is the denser, weaker layer beneath the lithospheric mantle. It lies between about 100 kilometers (62 miles) and 410 kilometers (255 miles) beneath Earth’s surface. The temperature and pressure of the asthenosphere are so high that rocks soften and partly melt, becoming semi-molten. The partially melted rock flows very slowly in convection currents.
The very slow motion of lithospheric plates “floating” on the asthenosphere is the cause of plate tectonics, a process associated with continental drift, earthquakes, the formation of mountains, and volcanoes. In fact, the lava that erupts from volcanic fissures is actually the asthenosphere itself, melted into magma.
THE UPPER MANTLE (Transition Zone)
In the transition zone, rocks do not melt or disintegrate. Instead, their crystalline structure changes in important ways. Rocks become much, much more dense.
Perhaps the most important aspect of the mantle’s transition zone is its abundance of water. Crystals in the transition zone hold as much water as all the oceans on Earth’s surface.
Water in the transition zone is not “water” as we know it. It is not liquid, vapor, solid, or even plasma. Instead, water exists as hydroxide.
THE LOWER MANTLE
The lower mantle extends from about 660 kilometers (410 miles) to about 2,700 kilometers (1,678 miles) beneath Earth’s surface. The lower mantle is hotter and denser than the upper mantle.
The lower mantle is much less ductile than the upper mantle and transition zone. Although heat usually corresponds to softening rocks, intense pressure keeps the lower mantle solid.
Geologists do not agree about the structure of the lower mantle.
The core makes up 15% of the Earth’s volume. Earth’s core is the very hot, very dense center of our planet. The ball-shaped core lies beneath the cool, brittle crust and the mostly-solid mantle. The core is found about 2,900 kilometers (1,802 miles) below Earth’s surface, and has a radius of about 3,485 kilometers (2,165 miles).
THE OUTER CORE
This part of the core is also made from iron and nickel, just in liquid form. It sits some 5,180 to 2,880 kilometers (3,220 to 1,790 miles) below the surface. Heated largely by the radioactive decay of the elements uranium and thorium, this liquid churns in huge, turbulent currents. That motion generates electrical currents. They, in turn, generate Earth’s magnetic field. For reasons somehow related to the outer core, Earth’s magnetic field reverses about every 200,000 to 300,000 years. Scientists are still working to understand how that happens.