Download 8th Grade - Mountain building!

8TH GRADE - MOUNTAIN BUILDING!
DYNAMIC EARTH U4L3
THE MOVEMENT OF TECTONIC PLATES CAUSES STRESS!
 Stress = the amount of force per unit placed on an object
 When a rock is placed under stress it can deform.
 What is deformation?
 When rocks bend they form ______________.
 When rock break it forms ______________.
WHAT ARE TWO KINDS OF FOLDS?
Mojave Desert, California
SYNCLINE OR ANTICLINE?
Saint-Godard-de-Lejeune, Canada
Rocky Mts. Alberta, Canada
New Jersey
WHAT ARE THE THREE KINDS OF FAULTS?
 Just list them. We will describe them on the next few slides.
NORMAL FAULTS
REVERSE FAULT
STRIKE-SLIP FAULTS
FOLDED MOUNTAINS
Mt. Kidd: Canadian Rockies
VOLCANIC MOUNTAINS
Mt. Fuji: Japan
FAULT-BLOCK MOUNTAINS
Teton Range: Wyoming
TH
8
GRADE - VOLCANOES
DYNAMIC EARTH U4L4
VOLCANO
 Opening in earth that erupts gases, ash, and/or lava.
- Volcanic Eruptions
HOW DO VOLCANOES FORM?
 Rocks in mantle melt to form _MAGMA__ which
rises because it is less dense than surrounding rock.
(Pressure can also help force magma upward.)
 Volcanoes form when magma flows out of surface
opening called a ____volcano___; a depression
around vent is called a __vent__.
PARTS OF A VOLCANO
WHAT COMES OUT OF A VOLCANO?
 Lava
 High viscosity lava – resistant to flow
 Explosive, forms steeper-sloped volcanoes
 Low viscosity lava – flows easily, forms low sloped volcanoes
 No explosions
 Pyroclastic materials / pyroclastic flow – hot ash and bits of rock,
hardened lava
TYPES OF VOLCANOES
1. Shield Volcano
-broad base, gently sloping sides
- Form from mild eruptions – not explosive
- Layers of low-viscosity lava building up over time
- Ex: Hawaiian Islands
2. Cinder Cone Volcano
- Steep sides
- Made of pyroclastic materials
- High viscosity lava
- Explosive!
- Can form side vents
- Ex: Paracutin in Mexico
Paricutin
Paricutin
3. Composite Volcano
-alternating layers of pyroclastic
material and lava
-steep AND broad
SO BIG!
-has both explosive and not explosive
eruptions
Mount
Rainer
Mt. Rainier
- Volcanic Landforms
VOLCANIC FEATURES: FISSURES AND LAVA PLATEAUS
 Fissures – giant cracks in Earth’s surface (land and ocean) –
several kilometers long
 Fissure eruptions have no central opening – lava flows out of
entire length of fissure
 Form lava plateau – thick, flattened layer of cooled lava
VOLCANIC FEATURES: CRATERS AND CALDERAS
 Crater – opening at top of volcano
 Caldera – formed when magma chamber below volcano collapses
 Ex: Crater Lake, OR
- Volcanic Landforms
WIZARD ISLAND IN CRATER LAKE
WHERE DO VOLCANOES FORM?
1. DIVERGENT BOUNDARIES
 Fissures most common here
 Plates stretch out, asthenosphere bulges up, magma comes out
 Most are on ocean floor
 Forms at mid-ocean ridges
 Iceland – volcanic activity on land where plates diverge
Volcano at Divergent Boundary
WHERE DO VOLCANOES FORM?
2. CONVERGENT BOUNDARIES
 Friction causes heat at subduction zones, melts magma
 Magma is highly viscous (resistant to flow), THICK
 Erupts EXPLOSIVELY!
 Composite volcanoes
 Ex. Cascade Range – includes Mt. St. Helens
Volcano at Convergent Boundary
Formation of Volcano
WHERE DO VOLCANOES FORM?
3. HOT SPOTS
 Mantle plume (column of superhot mantle) rises through
asthenosphere
 Forms shield volcanoes
 As plate moves, chains of volcanic islands form
 Usually not explosive
 Magma is not viscous, it’s runny
 Ex: Hawaii
 Why are the
Hawaiian
Islands in a line?
Will there be
more?
Location Map of Volcanoes