Volcanic EruptionsTephra is the fancy science word for all the fragments that a volcano spits out. Cinder, ash, chunks of rock.

Lightning?? Yep, lightning! During an eruption, particles of tephra bump into each other and they build up electric charge. Just like a thunderstorm!

A surge is a blob of finer particles that moves much faster than the rest of the cloud.

A cinder fall is just like a springtime rainstorm.

Lava fountains sound so pretty! And they are pretty, actually, as long as you are watching these glowing-hot sprays of liquid rock from a safe distance.

In case lava, tephra surges, and lightning aren’t exciting enough, we also need volcanic bombs to shoot out. These are super hot rocks that are on the verge of melting.

Pyroclastic flow is a surge of material that rushes down the hill and demolishes anything in its path. The shape of the volcano is created by its own eruptions as layers of ash and lava settle and cool.

In the magma chamber, a pocket of melted rock is trapped. Liquid rock is less dense than the solid rock around it, so it acts like a bubble trying to float to the top. Pressure builds until... rumble rumble KABOOOOOOM!!

Stratosphere is the second layer from the surface. Here, the temperature actually rises as we go higher, until we reach the top of the stratosphere. The air is really thin here, which is why jet planes and weather balloons don’t go any higher than this.

This is where we find the Ozone Layer, an area where Oxygen molecules hang out in groups of three. It turns out that O3 is terrific at absorbing UV radiation from the sun. For life on earth, this is important! We need some UV light to survive, but too much damages our skin cells.

The Atmosphere

Tropo means “change”. The troposphere is named after change because of its constantly shifting weather. The most dense part of the atmosphere, this is where we all live and breathe.

Exo means “outer”. This is the transition between our atmosphere and outer space.

The thermosphere is a weird place! Therm means heat. In the thermosphere, the energy from the sun causes the molecules here to zip around really fast, and faster movement = more heat. So theoretically, this area should be very hot. BUT! The weird thing is that there are so few molecules in this layer that the air actually feels unbelievably cold. Meteoroids here don’t hit enough molecules to cause them to burn up.

Meso means “middle”. Here, the air is too thin to support planes or even clouds, but there are enough air molecules to burn up speeding meteoroids. (Down on Earth, we see these as shooting stars.)

Ocean Zones

Sunlight ZoneThis ocean zone may be the smallest in terms of water volume, but it is the home to the majority of ocean life!

Twilight ZoneNot just the name of a classic television show, and nothing to do with vampires. This zone is called twilight because the ocean gets darker the deeper you go. Plants can’t grow here, but this zone is great for bioluminescent sea creatures.

Midnight ZoneTHIS is where creatures from a sci-fi show should come from. This is the deep ocean, where it’s so perpetually dark that most sea creatures have evolved to produce their own light. Food sources are so scarce that creatures do whatever it takes to secure a meal, including enticing prey to their wild strobe-lit dance parties.

AbyssThe pressure at the bottom of the ocean is so extreme that we can’t explore it without building very specialized vehicles. We have seriously studied Mars in more detail than our deepest oceans.

HadalNamed after Hades, the underworld in Greek mythology. This is where we find the deepest trenches (like the Mariana Trench) of the ocean floor.

The Earth’s (Amazing!) Fossil Record

Cenozoic EraThe Cenozoic Era is made up of three periods: Quaternary (what we’re currently in — also known as the Age of Humans), Neogene, and Paleogene. It’s a great time to be a mammal or a fish or pretty much anything other than a non-avian dinosaur.

Paleozoic Era

In this era, fossils tell the story of the first explosion of complex life on Earth. Within a very short time (in geology, “short” means an unbelievably long period of time that is much shorter than other mind-blowing periods of time), the number of different types of critters increased by a lot. Fossils with vertebrates — including fish, insects, and the first creatures on land — are all found together in this era.

Mesozoic EraThe age of dinosaurs! Pretty cool, right? Dinosaurs didn’t all live at the same time! T-Rex evolved long after Stegosaurus was extinct. And the entire time, mammals, fish and reptiles still existed — just in small forms.

EXTINCTION EVENT

EXTINCTION EVENT

The history of the Earth goes back further than our brains can imagine, so to make it easier to talk about, we divide time into big chunks called eras.

River SystemsUpland is surrounding land that doesn’t flood because it’s at a higher elevation.

We think of flooding as a disaster, but rivers have been flooding as part of their natural cycle for millions of years.

The flood plain around a river is the lowest elevation. It’s where the river will flood on any given year. Be careful about building a house here! Some people actually build their house up on stilts so it’s safe from floodwaters.

We measure floods in terms of how often they are likely to happen.

A 50-year floodplain is the area that is close enough to the river that it sometimes floods, but it’s elevated enough that it only has a 2% chance of flooding every year.

A 100-year floodplain has a 1% chance of flooding each year.

A 500-year floodplain is almost never underwater! Every year there’s only 0.2% chance of floodwaters swelling high enough to reach this area.

A tributary is a smaller stream that joins up with a river.

Meander is when a river bends and curves back and forth across the landscape.

Oxbow lakes are formed when a meandering river cuts itself off, trapping some of the water from the meander.

Marshes and wetlands are unique ecosystems full of noisy wildlife. I know because I live alongside a marsh and it is basically an orchestra of weird-sounding frogs, toads, birds, bats, and bugs. We also have snakes, turtles, and fish but those are much quieter.

A levee is a wall that humans build to protect an area from flooding.

When an earthquake occurs, it releases a lot of energy in the form of waves. Love waves and Rayleigh waves travel along the surface. Primary waves and secondary waves travel down through the earth.

How An Earthquake Travels

People used to think that the core of the earth was hollow and maybe even inhabited. Now we know that it cannot be hollow because there are large areas where P waves and S waves can’t reach. This area is a shadow zone where the core of the earth blocks or deflects all waves.

On the opposite side of the earth, people won’t FEEL the earthquake, but sensitive instruments will detect some of the energy waves. But here’s the interesting thing: only P waves make it through. This is how we know that part of the earth’s core must be liquid. P waves can pass through liquid but S waves can’t.

Love waves are the vibrations that arrive first, though we usually don’t notice them. Dogs hear them!

Raleigh waves are the ones we feel and they are the most destructive. They roll like ocean waves.

The waves that go through the earth are called primary (arrive first) and secondary (second), or P waves and S waves for short. Instruments that are thousands of miles away will detect both kinds of waves.

It might not feel like it, but the earth beneath us is constantly moving. Most earthquakes happen when two tectonic plates try to slide past each other, and their jagged edges get stuck. Tension builds up until finally the plates give way and crack!