Meteorites, Meteoroids and Craters Not just any old hole in the ground!

Meteoroids Small rocks that are found in space are called meteoroids. Most of the shooting stars that you see at night are sand grain sized particles burning up in the earth’s atmosphere!

Meteor Showers Meteor showers occur when the earth passes through the debris left by a comet. Many well known meteor showers are named after the constellations they appear to be coming from. Perseids, Orionids, Geminids and the Leonids are few of the most common ones seen in the northern hemisphere.

Fireballs Larger meteors that can be seen for more than a second are called fireballs. These can be fist sized to boulder sized rocks traveling at great speed and burning up in the atmosphere.

Meteorites Rocks that survive their fall through the earth’s atmosphere are called meteorites. They are most commonly found in the deserts and antarctica They can be metallic, stony or stony- mettalic.

Asteroids Large, city block sized and bigger rocks are called asteroids. Because of their large size and great mass they are not slowed down by the earth’s atmosphere. These are a few of the larger asteroids that come close to the Earth. 59 km = 35 miles

Earth Craters Because of erosion, plate tectonics and its atmosphere Earth does not have a large number of craters. Most of the craters seen here have been mapped in the last 50 years.

Craters in the US Meteor Crater in Arizona was first thought to be a volcano. The diameter of the crater is 1.2 km and it is about 500 feet deep. It is thought to be 50,000 years old. It was formed by the impact of a large iron/nickel asteroid.

Canyon Diablo meteorite This 1069 lb. meteorite is a fragment of the giant meteorite that explosively formed Meteor Crater in Arizona

An aerial photograph of the 1.13-km-diameter Pretoria Saltpan impact crater (also known as the Tswaing Crater) in South Africa.

). The Holleford Meteorite Crater, Quebec, Canada was formed by an asteroid 100m in diameter, traveling at 20 km/sec. It impacted with a kinetic energy six times that of the object that formed the Barringer Crater. A 244 meter deep crater was blasted out of the rock. The depression filled with water to become a circular lake.

Lonar Crater, India 1.8 km wide, 52,000 years old

Gosses Bluff crater This crater is in the Northern Territory of Australia. It is 22 km (13.2 miles) in diameter and believed to be 142 million years old. The structure is deeply eroded and only the central uplifted portion of the crater is still clearly visible.

Australian Craters cont. Wolfe Creek Crater is located in Western Australia. 300,000 years old and approx..6 miles in diameter. The floor lies 55 meters below the rim of the crater. The rim of the crater rises 25 meters above plain. The native people call the crater "Kandimalal" and have been aware of it for thousands of years

The Chicxulub Crater in Yucatán Geologists, searching in 1987 for limestone sinkholes, discovered the perimeter of the 200 km-wide Chicxulub impact crater. This impact, 65 million years ago, may have played a major role in the extinction of the dinosaurs. This crater, variously estimated at km in diameter, is the 3rd largest impact structure known on Earth.

Gravity map of Chicxulub crater, showing outline of Yucatán coast. White dots are cenotes, often concentrated along the crater rim (after Hildebrand et al 1995).] Many researchers have tried to measure the crater’s size. Hildebrand (1991) located two concentric rings which suggested an outer rim of 180 km (108 miles), Sharpton (1993) found 4 concentric rings indicating a 200 km (120 mile)-wide basin with inner rings 104 and 154 km in diameter, and a 300 km (180 mile) periphery. Hildebrand (1995), while mapping shallow structures in the crater, rather than the deeper underlying strata, showed six rings within his proposed 180 km diameter.

Chicxulub crater 150 to 180 mile wide crater. 10 miles deep Event occurred 65 million years ago. This is the same time that the Dinosaurs disappeared from the planet. It is covered by many layers of sedimentary rock It released 100 trillion tons of TNT The shock wave and firestorm following this event may have destroyed up to half of the flowering plant species on earth.

Dinosaur doom?? This crater resembled other multi-ringed craters, on Venus, Mercury, Europa, or the Moon. Beads of altered glass called tektites related to the formation of Chicxulub Crater have been found in Belize 480 km (288 miles) from the crater. Similar tektites, formed from the heat of the Chicxulub impact, are scattered as far afield as Haiti and north Mexico

Tektites

Tektite Fields of the Earth Most tektites are found in these 4 fields. Three of the fields (#2,# 4 and #3) have known impact craters associated with them. The Australian/Asian field (#1) alone covers 10% of the Earth’s surface. The properties of these strange rocks can only be explained by a meteor impact.

Top Ten known craters on the Earth. NameState/ProvCountryDia. (km) Age (millions of years) visible VredefortS. Africa Yes SudburyOntarioCanada Yes ChicxulubYucatanMexico No Manicouagan QuebecCanada Yes PopigaiRussia Yes AcramanS. Aust.Australia Yes Chesapeake Bay VirginiaUSA No Puchezh- Katunki Russia No MorokwengS. Africa No KaraRussia No

Vredefort crater in South Africa This is the largest known crater on the planet. It is 300 km wide (180 miles) and it is 2 billion years old!

Sudbury Crater, Ontario, Canada 250 km (150 miles) in diameter, 1.8 billion years old

Sudbury Crater, Ontario

Another Canadian lake revealed to be an old crater! Manicouagan, 100 km (60 miles) diameter, 200 million years old

Popigai crater, Russia 100 km (60 miles) in diameter, 30 million years old

Acraman Crater South Australia 90 km (60 miles) in diameter, 450 million years old

Chesapeake Bay Crater (85 km), 35 million years ago. The Research ship Glomar Challenger discovered this crater in 1983 while digging cores in the sediment of the bay. It is 1.3 km below the surface.

Beaverhead Crater, Challis, Idaho 60 km (36 miles) in diameter, 550 million years old

Can you find the ancient crater?

Find this crater located in Africa!

Clearwater West (36 km) and Clearwater East (27 km). Both were formed 270 million years ago.

Mistastin Lake, Newfoundland and Labrador, Canada. 28 km diameter, 38 million year old

Richat Structure, Oadane, Mauritania. Sahara 38 km diameter (23 miles)

Teague, Western Australia. Diameter = 28 km age 1.7 billion years.

Examination of the bottom of this 5 km wide lake in Canada revealed it to be a crater!

Rotor Kamm, Namibian Desert, Africa. 2.5 km diameter, 3.5 million years old

Roter Kamm from the side. Erosion has drastically affected this crater.

Bosumtwi, Ghana km diameter and 1.3 million years old

Kara-Kul, Tadzhikistan. 45 km in diameter, 10 million years old.

These craters are on Venus! The pictures were taken by the Magellan space probe.

Yuty Crater, Northern Hemisphere of Mars Diameter 19 km Note the ejecta blanket of frozen water!

This large carter on the Martian moon Phobos nearly split this small moon in two!

Copernicus crater on the Moon!

A large multi-ring crater on Mercury.

The Great Extinctions. People feel that large impacts may explain why some of these happened.

Great Marine Extinction Percentages Name Ma Families Genera All Species Land Species Cretaceous -Tertiary (KT) % of vertebrate families Triassic - Jurassic unclear Permian -Triassic % of land species Late Devonian little known Ordovician – Silurian nonexistent

Families becoming extinct In general, at any given time, about 5% of all species are going extinct; this is the "background extinction rate". In the KT event 85% of species were lost, while only 47% of genera, 16% of families, 10% of orders and 1 out of 82 classes went extinct. No phyla were lost