Underground Levels
4. The Magma Core
At 4000 kilometres down is another place even the Drow dare not to tread.
1a. The Outer Core
1b. The Inner Core
2. Lava
3. Heat Game Effects
4. Cities
| 1a. The Outer Core |
| The outer core of the Earth is a fluid layer about 2,300 km thick and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. Its outer boundary lies 2,890 km beneath Earth's surface. The transition between the inner core and outer core is located approximately 5,150 km (3,200 mi) beneath the Earth's surface. Unlike the inner core, the outer core is not solid. This is also referred to as the "liquid core". Estimates for the temperature of the outer core are about 3,000–4,500 K (2,730–4,230 °C; 4,940–7,640 °F) in its outer regions and 4,000–8,000 K (3,730–7,730 °C; 6,740–13,940 °F) near the inner core. Evidence for a fluid outer core includes observations from seismology which shows that seismic shear-waves are not transmitted through the outer core. Because of its high temperature, modelling work has shown that the outer core is a low viscosity fluid that convects turbulently. Eddy currents in the nickel iron fluid of the outer core are believed to influence the Earth's magnetic field. The average magnetic field strength in the Earth's outer core was measured to be 2.5 millitesla, 50 times stronger than the magnetic field at the surface. The outer core is not under enough pressure to be solid, so it is liquid even though it has a composition similar to that of the inner core. Sulphur and oxygen could also be present in the outer core. As heat is transferred outward toward the mantle, the net trend is for the inner boundary of the liquid region to freeze, causing the solid inner core to grow. This growth rate is estimated to be 1 mm per year. |
| 1b. The Inner Core |
| The Earth's inner core is the Earth's innermost part. It is primarily a solid
ball with a radius of about 1,220 kilometres, which is about 70% of the Moon's
radius. It is composed of an iron–nickel alloy and some light elements. The
temperature at the inner core boundary is approximately 5700 K (5400 °C). Based
on the relative prevalence of various chemical elements in the Solar System, the
theory of planetary formation, and constraints imposed or implied by the
chemistry of the rest of the Earth's volume, the inner core is believed to
consist primarily of a nickel-iron alloy. Pure iron was found to be denser than
the core by approximately 3%, implying the presence of light elements in the
core (e.g. silicon, oxygen, sulphur) in addition to the probable presence of
nickel. Further, if the primordial and mostly fluid (still forming) earth
contained any significant mass(es) of elements denser than iron and nickel,
namely the white (appearance) precious metals (and a few others) except silver,
specifically the siderophile elements (those marked red on that table) then
these would necessarily have differentiated to the very centre of the core into
concentric nested spheres by Planetary differentiation. The most dense (and
stable, i.e. platinum, iridium, and osmium, (etc.) in order of density) of these
forming the innermost spheroid(s). While unstable elements of such
trans-iron/nickel density would have mostly decayed to iron/nickel/lead by the
time the earth formed a discrete core. The temperature of the inner core can be estimated by considering both the theoretical and the experimentally demonstrated constraints on the melting temperature of impure iron at the pressure which iron is under at the boundary of the inner core (about 330 GPa). These considerations suggest that its temperature is about 5,700 K (5,400 °C; 9,800 °F). The pressure in the Earth's inner core is slightly higher than it is at the boundary between the outer and inner cores: it ranges from about 330 to 360 gigapascals (3,300,000 to 3,600,000 atm). Iron can be solid at such high temperatures only because its melting temperature increases dramatically at pressures of that magnitude. A report published in the journal Science concludes that the melting temperature of iron at the inner core boundary is 6230 ± 500 K, roughly 1000 K higher than previous estimates. The Earth's inner core is thought to be slowly growing as the liquid outer core at the boundary with the inner core cools and solidifies due to the gradual cooling of the Earth's interior (about 100 degrees Celsius per billion years). Many scientists had initially expected that the inner core would be found to be homogeneous, because the solid inner core was originally formed by a gradual cooling of molten material, and continues to grow as a result of that same process. Even though it is growing into liquid, it is solid, due to the very high pressure that keeps it compacted together even if the temperature is extremely high. It was even suggested that Earth's inner core might be a single crystal of iron. However, this prediction was disproved by observations indicating that in fact there is a degree of disorder within the inner core. Seismologists have found that the inner core is not completely uniform, but instead contains large-scale structures such that seismic waves pass more rapidly through some parts of the inner core than through others. In addition, the properties of the inner core's surface vary from place to place across distances as small as 1 km. This variation is surprising, since lateral temperature variations along the inner-core boundary are known to be extremely small (this conclusion is confidently constrained by magnetic field observations). Recent discoveries suggest that the solid inner core itself is composed of layers, separated by a transition zone about 250 to 400 km thick. If the inner core grows by small frozen sediments falling onto its surface, then some liquid can also be trapped in the pore spaces and some of this residual fluid may still persist to some small degree in much of its interior. Because the inner core is not rigidly connected to the Earth's solid mantle, the possibility that it rotates slightly faster or slower than the rest of Earth has long been entertained. Growth of the inner core is thought to play an important role in the generation of Earth's magnetic field by dynamo action in the liquid outer core. This occurs mostly because it cannot dissolve the same amount of light elements as the outer core and therefore freezing at the inner core boundary produces a residual liquid that contains more light elements than the overlying liquid. This causes it to become buoyant and helps drive convection of the outer core. The existence of the inner core also changes the dynamic motions of liquid in the outer core as it grows and may help fix the magnetic field since it is expected to be a great deal more resistant to flow than the outer core liquid (which is expected to be turbulent). Speculation also continues that the inner core might have exhibited a variety of internal deformation patterns. This may be necessary to explain why seismic waves pass more rapidly in some directions than in others. Because thermal convection alone appears to be improbable, any buoyant convection motions will have to be driven by variations in composition or abundance of liquid in its interior. |
| 2. Lava |
| Molten lava has a base damage of 2D6. This is the level of
damage sustained if a character walks on lava or is splashed by lava. If a
character has a limb or more of their body covered by lava, it causes 5D6
damage. If half or more of his body is covered by lava, then the character
suffers 10D6 damage. Finally, if his entire body is immersed in lava, he
suffers 20D6 damage. The character continues to suffer this damage each
round, until he has been removed from the lava. As lava may stick to the character, it may be difficult to naturally remove the lava from a character who has been immersed in a pool of lava. Although armour provides some protection from splash damage, the lava can flow through and behind the character’s armour once he is substantially covered. Characters exposed to burning oil, bonfires, and noninstantaneous magic fires might find their clothes, hair, or equipment on fire. Spells with an instantaneous duration don’t normally set a character on fire, since the heat and flame from these come and go in a flash. Characters at risk of catching fire are allowed a Reflex save to avoid this fate. If a character’s clothes or hair catch fire, he takes D6 points of damage immediately. In each subsequent round, the burning character must make another Reflex saving throw. Failure means he takes another D6 points of damage that round. Success means that the fire has gone out. (That is, once he succeeds on his saving throw, he’s no longer on fire). A character on fire may automatically extinguish the flames by jumping into enough water to douse himself. If no body of water is at hand, rolling on the ground or smothering the fire with cloaks or the like permits the character another save with a +4 bonus. Those unlucky enough to have their clothes or equipment catch fire must make Reflex saves for each item. Flammable items that fail take the same amount of damage as the character. Sometimes volcanic activity heats water and mud to scalding temperatures. Bubbling pools of mud and geysers of boiling water trap the unwary. Boiling mud and water both cause +3 damage to a character (+6 damage for immersion of a limb, +9 damage for immersion of a torso, and +12 damage for total immersion). Of course, mud pools and hot springs of lesser temperature are not dangerous, and some characters frequently bathe in these for medicinal benefit. The noxious fumes from magma affect
anyone who comes within 15 paces
of a crater or river of lava. This has two Characters caught in an eruption
may be swamped by lava, crushed by
falling rocks, overcome by fumes, or buried |
|
3. Heat Game Effects |
|
| Even characters who are merely close to lava can take damage from the heat. Characters who approach within 27 metres of molten lava suffer +3 heat damage each round. | |
| Temp | Effect |
| 310C | Discomfort. Shortness of breath. Sweating. |
| 400C | Blurry vision. Breathing is difficult. 50% chance of fainting every 8 minutes. -1 on all combat and skill rolls. |
| 500C | Can’t open eyes. 80% chance of fainting every minute. D6 damage every 2 rounds. -3 on all combat and skill rolls. |
| 1100C | Blind while in the area. 80% chance of fainting every 30 seconds. 2D6 damage per round. Can’t do anything. |
| 1500C | Unbearable pain. Can’t breathe. 90% chance of fainting per round. 3D6 damage per round. Anything combustible ignites in 4 rounds. |
|
Extreme heat also reduces
INT thinking ability by -1 point per 10C
over 400C when in direct exposure. Thermal and Infravision is useless once the temperature reaches over 500C due to all the thermal drafts in the air. Water boils at 1000C causing steam within the immediate area and reducing visibility to 15 metres or less. |
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| 4. Underground Cities and Subterranean Races key | |
| The following are all cities (with the exception of the Starstone) which float on top of the liquid outer magma core on occasion coming into contact with each other. | |
| City | Races |
| Crystallion | Gemzanite |
| Moltar | Terranean |
| Starstone | Magmanite |
| Zardeth | Mineroid |
| The Underground Sourcebook | The Shallow Depths | The Middle Depths | The Deepest Depths |