25.3 & 25.4 Flashcards
what is the boundary that marks the density change between layers?
discontintunity
how are discontintunity identified
using sizemicwaves
what are shadow zones
aries where no sizemicwaves are recording
another tearm for shadow zones
dead zone
between what degrees do shadow zones fall
105- 140 degrees
Is the outer core a liquid or a solid?
liquid
is the inner core a solid or a liquid? why
solid because of preacher.
what make up the lithosphere?
the crust and uppermost mantle.
what is the asthenosphere.
a plastic like layer witch Earths plates move.
what elements make up the mantle?
calcium aluminum lron magnesiem
the measure of a fluid’s resistance to flow
viscosity
the chemical compound silicon dioxide , SO2, conman in most magma
silica
volcano that are small, have highs in hundreds of meter ranges, short eruption cycle.
cinder cone
volcano that are broad, flat structures composed of layers upon layers of lava flow.
shield
volcanoes with large and steep-sided, often thousands of meters and tens of milometers across.
composite
how do volcanoes form
Molten, or liquid, rocks Magma is less dense than surrounding rock, causing it to rise.
why dose the magma reach earths surface
pressure conditions allow magma to move
why do volcano acre at plate boundaries.
eruptions occur where plates separate along a mid-ocean ridge or where plates collide along a subduction zone.
where are the most volcanic activity occur
along plate boundaries that surround the Pacific Ocean called the Ring of Fire.
why do they form here
because tectonic plates collide along subduction zones.
why do divergent volcanoes go unnoticed
because it occurs under water along mid-ocean ridges
can divergent volcanoes occur on land
volcanic activity occurs on land due to divergence, such as the East African Rift Valley.
what are hot spots
areas of volcanic activity where magma moves toward the surface in large, balloon like plumes
where are they hypothesized to originate
plumes originate near the core-mantle boundary
