Chapter 22 The Precambrian Earth Precambrian Time includes

Chapter 22 The Precambrian Earth

Precambrian Time: -includes everything Cambrian before the ____ period of the Paleozoic era 4 -length of about ___ billion years -88 % of earth’s history -much historical evidence destroyed

Barringer Crater n How did this feature form? Impact from meteor Do you think events like this were more or less common? more

Crust Formation n n Differentiation: -_______ heavier materials sink toward center lighter and _______ materials accumulate near surface

Precambrian _______ Shield – core of Archean and Proterozoic rocks; ____ rocks in North America; make up craton oldest

Laurentia _____ – ancient continent 1. 8 _____ billion years ago

Rodinia supercontinent _____ – first ________; 750 ______million years ago

Precambrian Atmosphere n n Volcanic Outgassing: -produced atmosphere of water vapor _______, carbon dioxide, nitrogen, and carbon monoxide, but not oxygen _____

Oxygen Producers n n Stromatolites: -large mats of ________ cynobacteria -dominated shallow oceans _____ of Proterozoic -nearly identical to those found in Australia ______ today

Oxygen Evidence n n n Banded Iron Formations: -alternating layers of chert _____ and iron oxides ________ -result of locally high oxygen _____ levels in early Proterozoic

Early Life _______ Prokaryote – single cell organism; no nucleus; only life before Proterozoic; includes cynobacteria Eucaryote – contains _____ nucleus; larger

Edicara Fauna – shallow marine organisms of 670 to 570 _____ Paleozoic era begins million years ago; extinct before_____

Chapter 22 Review n n What is the commonly accepted age of the Earth? 4. 6 billion years What is the process by which a planet becomes internally zoned? differentiation n What is the name of the first supercontinent that formed near the end of the Proterozoic? Rodinia

Chapter 22 Review (continued) n 4. Describe the major difference between Earth’s early atmosphere and explain how this occurred. Today’s atmosphere contains oxygen given off by photosynthetic plants. n 5. Describe the difference between prokaryotes and eukaryotes and tell which is older. Prokaryotes are smaller, have no nucleus, are less complex, and came first.