earth and space science chapter 5

What are convergent boundaries?

Two plates that move together. Oceanic lithosphere descends and is reabsorbed into mantle. Two continental blocks create a mountain belt

Explain continental- continental convergence.

Continental crust is buoyant. Neither plate subducts during continent-continent collisions. Folding and deformation of rocks. Mountain building

What happens at oceanic-continental convergence?

Continental lithosphere is less dense. Water from descending oceanic crust triggers partial melting of asthenosphere. Molten material is less dense and rises.

What is less dense, oceanic lithosphere or continental lithosphere?

Continental lithosphere.

What can convergent plate boundaries have?

Deep ocean trenches. Result of subduction.

Tectonic processes do what?

Deform crust and create major structural features

if the earth is 5 billion years old, why is the ocean crust no older 180 million years?

divergent plate boundaries created new ocean floors. new ocean floor is generated when mantle fills narrow fractures in oceanic crust.

if its ocean and ocean?

volcanic island arc

if its ocean continental?

volcanic mountain range

What is a rift valley?

A deep canyon along the crest of a ridge resulting from tensional forces

What does iceland have?

A rift valley

What is a hot spot? What is a hot-spot track?

An area of volcanism, high heat flow, and crustal uplift above a mantle plume. A hot spot track formed as the pacific plate moved over the hot spot.

Why does Hawaii have volcanoes if it's in the middle of nowhere if it's not near a plate?

Because it's on a hot spot.

Describe lithosphere.

Crust and uppermost coolest mantle. Oceanic lithosphere varies in thickness. Responds to forces by bending or breaking. Strong, rigid layer.

What are the three different boundaries?

Divergent, Convergent, and transform.

Example of continental rift?

East African rift valley

What are oceanic ridges?

Elevated seafloor with high heat flow and volcanism. Longest topographic feature of Earth's surface.

What is some of the evidence regarding ancient climates?

Evidence for glaciation on continents now at tropical latitudes. Can be explained by super continent located near the South Pole

What is some of the evidence to support the plate tectonics theory?

Evidence is from Deep Sea Drilling Project. Collect sediment and oceanic crust. Date fossils in sediment. Sediment age increases with distance from ridge. Sediment is thicker with increased distance from the ridge. Oldest seafloor is 180 million years old.

Example of transform plate boundaries?

Few transform faults cut through continental crust. San Andreas Fault

Transform plate boundaries ?

Form when two plates slide horizontally past one another. Transform faults. No lithosphere is destroyed or produced.

What are fracture zones of transform plate boundaries?

Linear breaks in the seafloor. Fracture zones contain active and inactive areas. Active faults occur between offset ridge segments

What are the two main layers on Earth?

Lithosphere and Asthenosphere

Which layer is broken into irregular plates?

Lithosphere. 7 major plates make up 94% of Earth. Plates move as rigid units relative to other plates

What is some of the evidence of fossils matching across the seas?

Mesosaurus, Glossopteris. Opponents explain fossil patterns by rafting, oceanic land bridges, and island stepping stones

What are continental volcanic arcs? What generates them?

Molten material is less dense and rises. One slab subducts under another at oceanic-oceanic convergent boundaries. Volcanism because of partial melting. Volcanic cones underlain by oceanic crust

What was created during the break up of Pangaea?

New ocean basins. Also, present plate motions can be used to predict future continental positions.

What are spreading centers?

New ocean floor is generated when mantle fills narrow fractures in oceanic crust

Why did wegnener's hypothesis of continental drift was met with criticism?

Objections were based on lack of mechanism for continental drift. Wegener proposed that tidal forces moved continents and that sturdy continents broke through thin oceanic crust

Convection?

Occurs as hot, less dense material rises and surface material cools and sinks.

What is continental rifting?

Occurs when divergent boundaries develop within a continent. Tensional forces stretch and thin the lithosphere. Brittle crust breaks into large blocks. Eventually become ocean basins. East African Rift demonstrates initial stage

What are the three types of convergent boundaries?

Oceanic + continental oceanic + oceanic continental + continental

Most divergent plate boundaries are associated with what?

Oceanic ridges

Most divergent plate boundaries are along what?

Oceanic ridges. New ocean floor is generated when mantle fills narrow fractures in oceanic crust

Describe the global oceanic ridge system.

Oceanographic exploration increased dramatically following WW2. Discovery of global oceanic ridge system. Earthquakes at great depths in western pacific ocean trenches. No oceanic crust older than 180 million years. This lead to developments of theory of plate tectonics. More encompassing theory than continental drift

Alfred Wegener did what?

Outlined the hypothesis of continental drift, single supercontinent of all of earth's land: Pangaea

What is seafloor spreading?

Process by which new seafloor is created along the ocean ridge system. New lithosphere is hot but cools and subsides with age and distance from the ridge system.

What is some of the evidence rock types and geologic features?

Rock types and geologic features match up. 2.2 billion year old igneous rocks in Brazil and Africa. Mountain belts end at coastlines and reappear across oceans

What is some of the evidence of the continental jigsaw puzzle?

Similarity between coastlines on opposite sides of the Atlantic. Opponents argued that coastlines are modified through time by erosion and deposition

The big bang theory only resulted in hydrogen and helium, where do our heavy elements come from?

The death of stars. When a star dies, gravity causes it to collapse on itself. When it collapses becomes very dense. Anything heavier than iron comes from that.

Describe convergent plate boundaries.

They occur when two plates move toward each other. Characteristics vary depending on subducting crust. Subducting zones. Lithosphere descends into the mantle.

How do plates and plate boundaries change?

Total surface area of Earth is constant. Size and shape of individual plates change. African and Antarctica plates are growing. Surrounded by divergent boundaries. Plate boundaries move and change through time.

What are transform plate boundaries?

Two plates slide past each other. No lithosphere is created or destroyed.

What are divergent boundaries?

Two plates that move apart. Upwelling of hot material from mantle creates new seafloor.

Describe the asthenosphere.

hotter, weaker mantle below the lithosphere. Rocks are nearly melted at this temperature and pressure. Responds to forces by flowing. Moves independently from lithosphere. Weak layer, rocks near their melting temperatures.