Intraplate Igneous Activity Hawaii’s Kilauea is Earth’s most active volcano; not found on a plate boundary Volcanism not near a boundary is said to be Intraplate Plume forms at core/ mantle boundary and rises to crust More than 40 identified hot spots active for millions of years

Yellowstone Park

Warm- Up Update your table of contents. 1. How old is Earth? 2. How would you measure the age of Earth? 3. Why would you want to study the age of Earth and evolution? TOC: 116. Geologic Time Month Scale Keywords: Uniformitarianism Law of Superposition Inclusion Unconformities Correlation

Early Attempts Around 500 BC, Xenophanes observed fossils and knew they must be very old. Circa 450 BC, Herodotus began examining the layers deposited by the Nile every year; said many thousands. 1779, Count de Buffon said 75,000 years Some scientists tried to use the saltiness of the ocean; 90 million years. Lord Kelvin used temperature to say million in Darwin wrote he “would die an unhappy man if Kelvin were right.”

Fossil vs. Non- Fossil Look over the list of items and place them on the fossil or non- fossil column on your paper. Several of you will come to the board. Raisin Seashell Small bone Small tooth Insect wing Leaf Apple slice with seeds Peanut Orange Seed Stick Hair

Rocks and Earth’s History Geologic Time scales were constructed to begin the approximation of Earth’s age. Most of the rock record has been erased through weathering and erosion. Earth is much older than we originally had thought.

Geology Sedimentary rock layers provide the most insight. Concept of uniformitarianism meant that processes observed today have happened for a very long time. Some processes are still observable while others are not.

Relative Dating Relative dating is the identification of rocks’ age from oldest to youngest. Tells us the sequence in which things occurred. Does not provide a numerical age.

Forming Rock Layers Weathering: rock breaks down Erosion: fragments and sediments carried away Deposition: sediments are placed in their new location

Law of Superposition Developed by Nicolaus Steno for relative dating. States that the oldest rock layers are found at the bottom and younger layers will be closer to the top.

Original Horizontality and Cross- cutting Steno also stated that rock layers would be deposited horizontally; thus flat layers would be undisturbed. Steno’s third observation was that any layers affected by a fault or igneous intrusion must be older than that event.

Inclusions Pieces of rock unit that are contained within another. Example: igneous intrusion forms and becomes exposed; new sedimentary layers from trapping igneous chunks (inclusions)

Unconformities No place on Earth is geologically complete Unconformities are missing layers from rock record. Uplifting and erosion cause layers to be removed. There are 3 basic types.

Unconformities 1. Angular unconformity occurs when deposition stops, deformation occurs, and erosion removes material. 2. Disconformities occur when erosion takes place between two sedimentary rock layers. 3. Nonconformities separate older igneous/ metamorphic rock from younger layers on top. ANIMATION

Correlation

Assignment Construct a timeline to represent the Earth’s history and significant events. Place the items on the right in order of when you think each happened first and where they happened relative to the beginning and end of the timeline. First monkeys First crocodiles First fish Vietnam War First dogs and cats First dinosaurs First fossil evidence of bacteria First cell with a nucleus First modern man First sharks First multicellular organism Oldest marine worms and jellyfish First flowering plants