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The Solar System
By studying the geology, climatology (weather) and hydrology (water) of the other planets and moons and comparing them to those that we see on Earth, scientists can gain a better understanding of how these systems work in general, not just here.
What we look for
Geology: Volcanos, faults, earthquakes, mountains, and Plate tectonics
Climatology: Clouds, weather, seasons, climate changes
Hydrology: Oceans, lakes, rivers, and groundwork
Terrestrial Planets
There are 4 which are Mercury, Venus, earth, and Mars. They all are largely composed of rocks and metals and they have layered interiors
Mercury - Closest to the Sun
GEOLOGY: Mercury is almost entirely dead but once had active volcanoes. It is the smallest planet and lost most of its internal heat long ago.
Today, it is covered with craters.
WATER: It has no liquid surface water.
ATMOSPHERE: It has an extremely thin and insignificant atmosphere.
Venus (2nd Planet)
GEOLOGY: Venus has many active volcanoes (confirmed in 2023) and is probably seismically active. It may have some form of plate tectonics.
WATER: None
ATMOSPHERE: A uniformly hot (867 °F), dense atmosphere composed of 96% carbon dioxide and highly corrosive sulfuric acid rain.
The Moon
GEOLOGY: The Moon was volcanically active in the distant past but is almost completely dead now. Only minor releases of gas and some small "lunarquakes" still occur.
WATER: No liquid surface water, but ice exists in some polar craters.
ATMOSPHERE: No significant atmosphere.
If it were not orbiting around Earth itself is would be considered at Planet
Mars (4th Planet)
GEOLOGY: Mars is almost completely dead, but some volcanic activity may still be possible.
Mars has the solar system's largest volcanoes, somewhat similar in type to those in Hawaii.
NASA's InSight lander detected marsquakes. Scientists used them to examine the planet's interior structure.
WATER: Mars has no liquid surface water today but had rivers and a shallow ocean in the past. Vast amounts of subsurface water still exist.
Mars also has polar ice caps.
ATMOSPHERE: It has a very thin atmosphere dominated by carbon dioxide. Seasonal planet-wide dust storms are common.
Gas Giant Planets
There are 2 gas giant planets in our solar system: Jupiter and Saturn.
They are largely composed of the gases hydrogen and helium, with small rocky interiors.
Gas giants do not have geology or oceans in the way we know them on Earth.
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Jupiter - the Largest Planet
ATMOSPHERE: Jupiter has high velocity winds and massive rotating weather systems, such as the Great Red Spot. Which are in the southern hemisphere, and storms in the northern hemisphere.
Although they appear similar to hurricanes (Low pressure systems), many of Jupiter's
"storms" are anticyclones (high pressure).
Jupiter's Moons
The only geological features to be found in the region are on a few of Jupiter's moons:
Io -The most volcanically active object in the solar system, with several active lava flows and lava lakes photographed and multiple eruptions recorded.
Europa - Has a liquid ocean beneath a thick layer of ice. It also has some kind of geologic activity, similar to ice-based plate tectonics.
Both the European Space Agency and NASA are sending missions to examine the moon in detail.
Saturn - the Ringed Planet
ATMOSPHERE: Generally similar to Jupiter
MOONS: Titan - the only moon with a significant atmosphere (mostly nitrogen) and weather. It has clouds and rainfall based on methane (natural gas). Methane rivers flow across its surface, and methane lakes are found in polar regions.
Enceladus - like Jupiter's moon Europa, it is believed to have an ice-covered ocean. A type of water-based volcanism (geysers) is active. Water has been seen erupting out of long fractures with enough energy to be ejected into space.
Ice Giant Planets
There are 2 ice giant planets in our solar system: Uranus and Neptune. Similar to gas giants, they have large amounts of hydrogen and helium in their atmospheres but have large mantles of ices above their small rocky cores. They are both relatively large and lack geology or oceans
Uranus
ATMOSPHERE: Similar to the gas giant planets, it has very high winds.
MOONS: Miranda - a geologically complex satellite with one of the highest cliffs (over 3 miles) in the solar system.
Neptune
ATMOSPHERE: Similar to Uranus, but warmer even though it is farther from the Sun.
MOONS: Triton - despite being extremely cold, it has active nitrogen geysers.
Pluto - A Dwarf Planet
Pluto has an atmosphere containing nitrogen, methane, ammonia, etc. It may freeze to the surface when it is far from the Sun.
NASA's New Horizons mission examined the planet, finding active nitrogen glaciers and evidence of other recent geologic activity.
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The Sun and the Earth
The Sun is very significant to life on Earth and the processes that affect it. It is the major source of Earth's surface heat, and its gravity has a significant influence on tides.
However, the relationship between our planet and the Sun changes over time, so the Sun's energy output.
The Suns Influence
Most weather systems and storms on Earth require heat energy to function. The majority of that comes from the Sun. Areas with more direct sunlight usually have more significant weather events - hurricanes in the tropics, tornadoes in mid-latitudes.
Water heated by the sun plays a major role in regional weather and global climate
Heat, Weather and Climate
Solar radiation plays the dominant role in Earth's weather and climate. Geologic heat (volcanic eruptions, plate tectonics) and heat from human activities often plays a more limited, but still significant, role.
Any changes in the relationship of the Earth and Sun will influence weather and climate. This could be on a daily, yearly or even longer cycle.
The Sun's Influence
The Earth is closer to the Sun in January than it is in July (by about 3 million miles). So why is winter cold?
The change in distance is not a major factor on a yearly basis. However, it does play a role over longer time periods when the situation is reversed (we are then closer in July). Long term climate can be significantly affected.
Seasonal Influence
The tilt of the Earth's axis is the primary cause of our seasons
Winter is cold because the Earth is tilted away from the sun, receiving less heat energy and days are shorter. Summer is warmer because the Earth is tilted towards the sun and days are longer. Regions near the equator have no significant seasons
The Sun and the Earth
Longer term variations have also been linked to the Sun. One example is The Little Ice Age (~15th to 19th centuries). This occurred during a period of lower-than-normal solar activity.
It's a bit more complex than that, however.
Volcanic activity almost certainly played a large part in this climatic event as well, possibly acting as a trigger to start it.
Changing Earth/Sun Relationships
To make things even more complicated, Earth's orbit around the Sun and the tilt of Earth's axis change over time. This is widely believed to have a major influence on long-term global climate.
Fortunately, these occur over very long periods of time and are of no significant concern In the near future 9-2-26
Near Earth Objects
Asteroids and Comets that can closely Approach the Earth
On Oct. 15th, asteroid 2022 UP6 may pass Earth at a difference of less than 105,000 miles, closer than the Moon( (239,000)
Impacts
It was once thought that impact events were not significant on Earth, either now or in the past. That changed in the late 20th century.
A large impact has recently been linked to massive global climate change that may have ended Earth's first ice age. Another impact may have triggered an ice age and a mass extinction event.
Near-Earth Objects (NEOs)
NEOs are asteroids or comets with orbits that either cross or closely approach the Earth. Most are small asteroids.
There may be thousands of them in our solar system with diameters of 1 kilometer or more. A collision with an object that size would cause severe changes to our planet's climates.
Significant impacts occur, on average, about once a century. Smaller ones have caused property damage and occasional injuries every few years.
Scientists have discovered over 42,000 NEOs so far, but most are very small. Only a few are considered (extremely slight) impact risks.
The Chelyabinsk Meteor
On February 15, 2013, a meteorite over 60 feet in diameter and over 10,000 tons exploded over the Ural Mountains in Russia. The impact shock wave injured over 1500 people.
NEOs: Asteroids (NEAS)
Since most are small, it has been difficult to detect most of them until very recently. They can be composed of rock, metals or both.
We now know that many asteroids are not very solid. They resemble large gravel piles held weakly together by gravity. Others are more metallic, made of iron and nickel.
NEOs: Comets (NECs)
They often travel at higher velocities than asteroids as they approach Earth's orbit. Comets are very similar to most asteroids except they contain much more ice.
Although far fewer in number, they are easier to detect than asteroids because of their brightness as the ice vaporizes due to solar heating.
NEC Impact
A collision with a comet would not be much different than one involving most asteroids.
Collisions are mainly about mass and velocity.
A large comet could be more deadly than a large asteroid, if it hit with a higher velocity.
NEOs: Impacts
In late 2021, NASA launched the DART (Double Asteroid Redirection Test) mission to the asteroid Didymos to impact with its small moon Dimorphos in late September 2022.
It was overwhelmingly successful - the impact changed the orbit of Dimorphos, demonstrating that NEOs can be redirected into safer orbits.
Throughout the solar system, we can see examples of collisions between planets (and their moons) and asteroids/comets.
The Moon is heavily cratered due to ancient impact events. So are most of the moons of every planet we have photographed. Mars and Mercury have many large craters.
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Craters on Earth
Once thought to be rare, scientists have now discovered over 194 confirmed impact craters on Earth.
The vast majority don't look like the Moon's craters, however. Erosion and other surface processes on Earth have buried or deformed most of our craters.
Barringer Crater in Arizona formed from an object about 150 feet in diameter.
An Ancient Impact in Ohio In southern Ohio, the remains of an ancient impact crater are located beneath Serpent Mound. The heavily eroded crater is about 5 miles in diameter.
20th Century Impact
In 1908, a comet exploded as it disintegrated over Tunguska, Siberia. Forests were destroyed over an area of 810 square miles, but no crater was left behind. This type of "impact" may be fairly common.
It is estimated that if the impact would have occurred a few hours later, Moscow might have been destroyed.
Importance of Plate Tectonics
The process of plate tectonics reshapes the Earth's surface over time and is the key to our understanding of:
Earthquakes, tsunami, volcanoes
Formation of major mountain ranges
Formation and evolution of ocean basins
Plate Tectonics and Earth's
Interior Structure
Unlike the earlier theory of continental drift, which only dealt with moving pieces of continental crust, plate tectonics involves the oceans as well. It also includes layers deeper in the Earth's interior- the lithosphere and the mantle.
Earth's Structure
CRUST:
Oceanic Crust - relatively thin, composed of basalt (a volcanic rock)
Continental Crust- thicker, made of granite. Basalt is denser than granite - this is very important in plate tectonic activity.
Deeper Earth Structure
MANTLE:
The mantle is separated from the crust by a boundary layer. The rocks in this layer are solid, but due to high temperatures and pressures, they flow very slowly.
The Earth's Core
OUTER CORE: The outer core is molten (liquid) and largely made of iron and nickel. The Earth's magnetic field originates here.
INNER CORE: The inner core is solid due to very high pressures. It is also mostly made of iron and nickel.
The Earth's Interior: Other Layers
The Lithosphere:
The crust and uppermost part of the mantle Rocks in this layer are solid and brittle
It is broken into pieces called plates
The Asthenosphere:
Part of the mantle below the lithosphere Rocks here are solid, but can flow slowly
Plate Tectonics - The Basics
Most of the large plates are named after the continents that they contain. The majority of the Pacific Ocean is also on one plate.
Smaller plates are just as important as large ones- they are responsible for many earthquakes and volcanoes, such as those in Washington, Oregon and northern California.
Plate Tectonics
Plates are made of oceanic lithosphere (basalt), continental lithosphere (granite) or both.
As the plates move, they interact with each other. This causes most of the world's large earthquakes, mountain ranges and major volcanoes.
Geologic activity is generally found at or near plate boundaries.
Divergent Plate Boundaries
Plates separate & move away from each other.
New plate material (oceanic lithosphere) is created as molten material fills in the rift.
Most are located in the oceans (central
Atlantic, caster Pacific, etc.), but some are on land (east Africa, Iceland).
Location of Earthquakes and Volcanos
The Mid-Atlantic Ridge
Although it is mostly underwater, there are several islands located on top of it, such as Iceland and the Azores. The average spreading rate is about 1 inch per year.
MAIN POINTS:
New oceanic plate material is created.
Small earthquakes are common, large ones are rare.
Volcanic activity is common.
Convergent Plate Boundaries
Plates collide with each other.
Plate material may be destroyed by subduction (if oceanic lithosphere is involved). Continental lithosphere does not subduct.
The type of geologic activity depends upon what kind of lithosphere is involved
Ocean-Ocean Convergent
One of the ocean floor plates is subducted.
Volcanic activity creates island-arcs on the surviving plate.
Earthquakes are common and may be large.
Examples – Japan, Indonesia, Aleutian Islands
Ocean continent convergent
The ocean floor plate is subducted, the continental plate is not.
Volcanoes form on the edge of the continent.
Earthquakes may be common and are potentially very large.
Examples – west coasts of North and South America
Continent Continent Convergent
Neither plate is subducted.
Significant volcanic activity is unlikely.
Earthquakes are relatively common and are potentially very large.
Major mountain ranges are created.
Examples – Himalaya Mts. and the Alps
MAIN POINTS:
Oceanic plate material is destroyed.
Continental plate material isn’t subducted.
Earthquakes of all sizes can occur.
Volcanic activity is common if ocean floor is involved, but not at continent-continent boundaries.
Transform Plate Boundaries
Plates “slide” past each other. No new plate material is created, no old plate material is destroyed.
Most are found on the ocean floor, but some are on land – The San Andreas Fault. Volcanoes do not tend to form here.
Motion along a transform plate boundary is not always smooth or continuous. Bends in the boundary can cause some sections to lock-up for long periods. This occurs near Los Angeles. Their last major earthquake was in 1857.
Unlike the other plate boundaries which are created by movements of the asthenosphere, these mainly exist to connect divergent and/or convergent boundaries to one another.
Despite their lack of volcanism, hot water (hydrothermal) systems are common and are major sites of exotic ecosystems.
MAIN POINTS:
Oceanic plate material is neither created nor destroyed.
Earthquakes of all sizes can occur, but extremely large ones are not common.
Significant volcanic activity is not likely.
THINGS TO REMEMBER
Divergent activity creates new ocean floor material.
Convergent activity destroys old ocean floor material.
Transform activity does not create or destroy plate material, it just moves it to new locations.
OTHER PLANETS AND MOONS:
Know the geology, oceans and atmospheric conditions of the other planets (and their notable moons), types of planets.
NEAR-EARTH OBJECTS (NEOs):
Asteroids and comets; impacts of NEOs; ancient impacts on Earth
PLATE TECTONICS:
The layers of the Earth – their composition and properties. What is significant about each layer.
Earlier versions of the theory (Continental Drift, etc.) and how they differ from plate tectonics.
PLATE TECTONICS:
Types of plate boundaries – geologic activity (volcanoes, earthquakes, etc.), what kind of motion occurs (separation, collision, etc.), creation and destruction of ocean floors.
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