Melting Rock

By John Walker,2014-12-03 03:03
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Melting Rock

Lava Flows & Pyroclastic Material

     fire + pieces blown out of volcano

    A: Lava Flows:

    1. ________________: ropey, cow pie lava

     From thin ________________

    2. ________________: rough, jagged, angular blocks of lava As lava freezes, it is being moved and breaks into pieces like glass.

    3. ________________: lava cools, contracts and splits at 60’ angles into hexagonal columns

    Mainly mafic lava

    4. ________________: blobs of lava quickly freeze underwater into “pillows”

B: Pyroclastic Material = Tephra = ________________

    1. Ash: < 2mm

    Most common pyroclastic

    Welds to form tuff

    Can be ejected 2 ways:

    A) ________________blown high into atmosphere & may travel 1000s of km before settling

    Can cool climate for years (ice age?)

    B) ________________= Nuee Ardente = Pyroclastic Flow: horizontal blast of ash and gasses

    +500C at 800 km/h

    2. ________________: 2-64mm = pebble size

    3. ________________: solid chunk of igneous rock >64mm blown out of volcano

    4. ________________s: blob of hot molten lava >64mm that is ejected, and partially freezes in flight.

    Volcano: ________________________________________________ ________________: depression near summit of volcano

    ________________: huge depression when most of volcano falls back into magma chamber

Types of Volcanoes

    1. ________________: composed of layers of pyroclastics and lava flows ________________rock usually (intermediate lava)

    Ex. Mt. Baker, Mt. Vesuvius, Mt Fuji

________________: mudflow of ash & water

    *Lahars and Pyroclastic flows pose the greatest human danger from volcanoes

    2. ________________: very, thick ________________lava moves up slowly under ________________

    Ex: Lassen Peak, CA, inside of Mt. St. Helens

3. ________________: short-lived “baby volcanoes consisting of just


    Form from initial eruption

    Up to 400 m high

    4. ________________: shallow sloped consisting of many low-viscosity ________________lava flows

    Largest volcanoes on Earth

    Ex: Hawaii (10 km high = BIG)

    5. ________________: large flows of low-viscosity ________________ lava that flow from long fissures (crack), rather than a single vent. Result of divergent boundaries

Melting Rock

    ;Mantle rock is s__________, magma is only present under certain conditions

    ;Factors that affect melting include

    ; T_____________


    ; V___________ (water, gas)


    ;G_____________ gradient, temperature i_____________ 25 celsius every km depth

    ;M______ t__________________ of rocks at the surface is between ___________ celsius

    ;Different m_________ melt at l___________ temperatures, this produces a p______ melt of m__________ and c____________ rocks


    ;P___________ i_________ with depth, causes a h________ melting t__________

Why Magma Rises

    1. F__________ E_____________: magma moves from _______ pressure at depth to ________ pressure at the surface

    2. S_________: d_____________ of magma by country rock (i.e. xenoliths) pushes magma up (like placing ice cubes in a glass of water)

Explosiveness of a volcano is dependent on:

    1. v____________ of magma: high viscosity s_______ the escape of g_______ which e________ greatly near the s____________

    2. “stickiness” of magma = “corking effect”. The stickier, the more p_________ it requires to erupt so when it does erupt…

    H___________ ______________ increases both viscosity & stickiness

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