What is the bottom of a tectonic plate like?

Are they relatively smooth or lumpy? Are they made of some consistent material? Are they somehow protected from, or actively interacting with, the magma underneath?


The boundary between the solid lithosphere and the partially melted/ductile asthenosphere is predominantly a thermal boundary. There can be significant compositional differences between the crust and the underlying mantle, depending on tectonic setting (i.e. oceanic crust is basically made of melted shallow mantle, while continental crust is chemically different in a number of ways). (Hofmann, 1988)
If, for example, you are talking about the boundary between the mantle and a subducted slab, the slab itself is essentially scraped flat by the overlying plate as it is subducted - but this is the top of the slab, not the bottom. (There are often heterogeneities in the structure along the fault itself, due to differences in lithology (rock type), structure of the individual plates, etc.) (Sage et al, 2006)
One thing that is important to understand about the mantle is that it is actually only about 10% melted. Think of it as a big sponge, with pockets and conduits of melt surrounded by crystalline solid. The main difference between the mantle and the crust is that the crust is cool enough that the rock is brittle - it can fracture and is resistant to strain. When the crust fractures it forms a fault along which earthquakes can occur. Meanwhile, because the mantle is hot and deep enough, the rock undergoes ductile deformation - it bends under stress - so earthquake fault ruptures do not occur (though seismic waves still travel through the mantle). (Hammond & Humphreys, 2000)

Here's a list of 155 free online programming/CS courses (MOOCs) with feedback(i.e. exams/homeworks/assignments) that you can start this month (October 2015)

Here's a list of 155 free online programming/CS courses (MOOCs) with feedback(i.e. exams/homeworks/assignments) that you can start this month (October 2015)
This is not the complete list of MOOCs starting in October 2015, just the ones relevant to this community. The complete list of courses starting in October 2015 can be found over at Class Central. You can see a much bigger list of these courses over at Class Central
BEGINNER(36)
Course NameStart DateLength (in weeks)ProviderRating
Introduction to CSS31st Oct, 2015NACoursera☆☆☆☆☆
An Introduction to Interactive Programming in Python (Part 1)3rd Oct, 20155Coursera★★★★★ (2469 reviews)
Introduction to Programming with MATLAB5th Oct, 20159Coursera★★★★★ (79 reviews)
Programming for Everybody (Python)5th Oct, 2015NACoursera★★★★★ (38 reviews)
Code Yourself! An Introduction to Programming5th Oct, 20155Coursera★★★★★ (2 reviews)
Introduction to Cyber Security5th Oct, 20158FutureLearn★★★★☆ (8 reviews)
HTML5.1x: HTML5 Part 1: HTML5 Coding Essentials and Best Practices5th Oct, 20156edX★★★★☆ (5 reviews)
Internet History, Technology, and Security5th Oct, 201510Coursera★★★★★ (21 reviews)
An Introduction to Interactive Programming in Python (Part 2)10th Oct, 20154Coursera★★★★★ (12 reviews)
Usable Security12th Oct, 20156Coursera★★★★☆ (4 reviews)
Begin Programming: Build Your First Mobile Game12th Oct, 20157FutureLearn★★★★☆ (6 reviews)
Data to Insight: An Introduction to Data Analysis19th Oct, 20158FutureLearn★★★★☆ (1 review)
CS101.2x: Introduction to Computer Programming, Part 220th Oct, 2015NAedX☆☆☆☆☆
Introduction à la programmation orientée objet (en Java)23rd Oct, 20157Coursera☆☆☆☆☆
BJC.2x: The Beauty and Joy of Computing (CS Principles), Part 226th Oct, 20157edX☆☆☆☆☆
Intro to Computer ScienceSelf paced12Udacity★★★★★ (50 reviews)
Intro to Java ProgrammingSelf paced16Udacity★★★☆☆ (10 reviews)
Mobile Web DevelopmentSelf paced6Udacity☆☆☆☆☆
DB: Introduction to DatabasesSelf paced11Stanford OpenEdx★★★★★ (5 reviews)
Make Your Own 2048Self pacedNAUdacity★★★★☆ (3 reviews)
Programming Foundations with PythonSelf paced6Udacity★★★★☆ (2 reviews)
Intro to HTML and CSSSelf paced3Udacity★★★★☆ (12 reviews)
JavaScript BasicsSelf paced3Udacity★★★★☆ (7 reviews)
How to Use Git and GitHubSelf paced3Udacity★★★★★ (15 reviews)
CS50x: Introduction to Computer ScienceSelf pacedNAedX★★★★★ (36 reviews)
Intro to Relational DatabasesSelf paced4Udacity★★☆☆☆ (2 reviews)
Networking: Introduction to Computer NetworkingSelf paced11Stanford OpenEdx★★★★★ (5 reviews)
CS101: Computer Science 101Self paced6Stanford OpenEdx★★★★☆ (6 reviews)
CS002x: Programming in ScratchSelf paced6edX★★★★☆ (3 reviews)
CS001x: MyCS: Computer Science for BeginnersSelf paced6edX★★★☆☆ (1 review)
DEV203x: Introduction to Bootstrap – A TutorialSelf paced3edX★★☆☆☆ (5 reviews)
LFS101x.2: Introduction to LinuxSelf paced8edX★★★★☆ (16 reviews)
CS005x: CS For All: Introduction to Computer Science and Python ProgrammingSelf paced14edX★★★★★ (2 reviews)
CS101.1x: Introduction to Computer Programming, Part 1Self paced9edX★★☆☆☆ (10 reviews)
COMP102.1x: Introduction to Java Programming – Part 1Self paced5edX★★★★☆ (3 reviews)
Learn Swift Programming SyntaxSelf paced3Udacity☆☆☆☆☆
INTERMEDIATE(96)
Course NameStart DateLength (in weeks)ProviderRating
Front-End Web UI Frameworks and Tools1st Oct, 2015NACoursera☆☆☆☆☆
Hadoop1st Oct, 2015NACoursera★★★★☆ (1 review)
Java Programming: Solving Problems with Software1st Oct, 2015NACoursera☆☆☆☆☆
Using Python to Access Web Data1st Oct, 2015NACoursera☆☆☆☆☆
iOS App Development Basics1st Oct, 2015NACoursera☆☆☆☆☆
Data Analysis Tools1st Oct, 2015NACoursera☆☆☆☆☆
Rails with Active Record and Action Pack1st Oct, 2015NACoursera☆☆☆☆☆
Responsive Web Design1st Oct, 2015NACoursera☆☆☆☆☆
Data structures: Measuring and Optimizing Performance1st Oct, 2015NACoursera☆☆☆☆☆
The Arduino Platform and C Programming1st Oct, 2015NACoursera☆☆☆☆☆
Programming Mobile Services for Android Handheld Systems: Concurrency5th Oct, 20154Coursera★★★★★ (1 review)
Statistical Inference5th Oct, 20154Coursera★★☆☆☆ (10 reviews)
Regression Models5th Oct, 20154Coursera★★★☆☆ (8 reviews)
Practical Machine Learning5th Oct, 20154Coursera★★★☆☆ (10 reviews)
Developing Data Products5th Oct, 20154Coursera★★★★☆ (4 reviews)
Introduction to Genomic Technologies5th Oct, 20154Coursera★★★☆☆ (6 reviews)
Bioconductor for Genomic Data Science5th Oct, 20154Coursera☆☆☆☆☆
Python for Genomic Data Science5th Oct, 20154Coursera★★★★☆ (4 reviews)
Statistics for Genomic Data Science5th Oct, 20154Coursera☆☆☆☆☆
CS169.1x: Engineering Software as a Service (SaaS), Part 15th Oct, 20159edX★★★★☆ (10 reviews)
Algorithms: Design and Analysis, Part 15th Oct, 20156Coursera★★★★★ (35 reviews)
Introduction to Software Product Management5th Oct, 2015NACoursera☆☆☆☆☆
Machine Learning5th Oct, 201511Coursera★★★★★ (110 reviews)
The Data Scientist’s Toolbox5th Oct, 20154Coursera★★★☆☆ (90 reviews)
R Programming5th Oct, 20154Coursera★★★☆☆ (140 reviews)
Getting and Cleaning Data5th Oct, 20154Coursera★★★☆☆ (25 reviews)
Exploratory Data Analysis5th Oct, 20154Coursera★★★★☆ (14 reviews)
Reproducible Research5th Oct, 20154Coursera★★★★☆ (10 reviews)
Process Mining: Data science in Action7th Oct, 20158Coursera★★★★☆ (6 reviews)
Principles of Computing (Part 2)10th Oct, 20154Coursera★★★★☆ (4 reviews)
Algorithmic Thinking (Part 2)10th Oct, 20154Coursera★★★★★ (1 review)
Software Security12th Oct, 20156Coursera★★★★★ (14 reviews)
Cryptography12th Oct, 20157Coursera★★★★☆ (5 reviews)
M101J: MongoDB for Java Developers13th Oct, 20157MongoDB University★★★★☆ (10 reviews)
M101JS: MongoDB for Node.js Developers13th Oct, 20157MongoDB University★★★★☆ (4 reviews)
M101N: MongoDB for .NET Developers13th Oct, 2015NAMongoDB University★★★★☆ (2 reviews)
M101P: MongoDB for Developers13th Oct, 20157MongoDB University★★★★★ (2 reviews)
M102: MongoDB for DBAs13th Oct, 20157MongoDB University★★★★☆ (6 reviews)
M202: MongoDB Advanced Deployment and Operations13th Oct, 20157MongoDB University★★★★★ (2 reviews)
PH525.1x: Data Analysis for Life Sciences 1: Statistics and R15th Oct, 20154edX★★★★☆ (6 reviews)
FP101x: Introduction to Functional Programming15th Oct, 20157edX★★★★★ (4 reviews)
6.00.2x: Introduction to Computational Thinking and Data Science20th Oct, 20159edX★★★★☆ (6 reviews)
Cryptography I26th Oct, 20156Coursera★★★★★ (25 reviews)
Software Processes and Agile Practices26th Oct, 2015NACoursera☆☆☆☆☆
Data Warehouse Concepts, Design, and Data Integration29th Oct, 2015NACoursera☆☆☆☆☆
DEV204x: Programming with C#29th Oct, 2015NAedX★★★★☆ (5 reviews)
Algorithms, Part II30th Oct, 20156Coursera★★★★★ (9 reviews)
Design of Computer ProgramsSelf paced8Udacity★★★★☆ (9 reviews)
Web DevelopmentSelf paced12Udacity★★★★★ (16 reviews)
Programming LanguagesSelf paced8Udacity★★★☆☆ (7 reviews)
Intro to AlgorithmsSelf paced16Udacity★☆☆☆☆ (1 review)
Software TestingSelf paced4Udacity★★★★☆ (5 reviews)
Software DebuggingSelf paced8Udacity★★★★☆ (2 reviews)
Intro to Theoretical Computer ScienceSelf paced8Udacity★★★★★ (1 review)
Intro to Artificial IntelligenceSelf paced16Udacity★★★★☆ (5 reviews)
HTML5 Game DevelopmentSelf paced8Udacity★★★☆☆ (4 reviews)
Learning from Data (Introductory Machine Learning course)Self paced10Others★★★★☆ (2 reviews)
Intro to Hadoop and MapReduceSelf paced4Udacity★★★★☆ (8 reviews)
CS 8802, Artificial Intelligence for Robotics: Programming a Robotic CarSelf pacedNAUdacity★★★★★ (1 review)
Intro to Data ScienceSelf paced8Udacity★★★★☆ (7 reviews)
Data Wrangling with MongoDBSelf paced8Udacity★★★★★ (4 reviews)
Website Performance OptimizationSelf paced1Udacity★★★★☆ (2 reviews)
UX Design for Mobile DevelopersSelf paced6Udacity★★★★★ (2 reviews)
Developing Scalable Apps in JavaSelf paced8Udacity★★★★☆ (1 review)
Developing Android AppsSelf paced10Udacity★★★★★ (2 reviews)
Software Development ProcessSelf paced12Udacity☆☆☆☆☆
Computer NetworkingSelf paced12Udacity★★★★★ (2 reviews)
Practical Numerical Methods with PythonSelf paced17Others★★★★★ (2 reviews)
Object-Oriented JavaScriptSelf paced5Udacity★★★★★ (6 reviews)
Intro to AJAXSelf paced2Udacity★★★★★ (1 review)
Data Visualization and D3.jsSelf paced7Udacity★★★☆☆ (1 review)
HTML5 CanvasSelf paced2Udacity★★★★☆ (2 reviews)
Intro to iOS App Development with SwiftSelf paced4Udacity★★★★★ (4 reviews)
Intro to jQuerySelf pacedNAUdacity★★★★☆ (2 reviews)
Intro to Machine LearningSelf paced10Udacity★★★★☆ (5 reviews)
Full Stack FoundationsSelf paced3Udacity☆☆☆☆☆
Responsive Web Design FundamentalsSelf paced2Udacity★★★★☆ (3 reviews)
JavaScript TestingSelf paced2Udacity★★★★★ (1 review)
LPL: Language, Proof and LogicSelf paced15Stanford OpenEdx☆☆☆☆☆
iOS Networking with SwiftSelf paced12Udacity☆☆☆☆☆
Browser Rendering OptimizationSelf paced4Udacity★★★★☆ (1 review)
Developing Scalable Apps in PythonSelf paced6Udacity★★★★☆ (1 review)
iOS Persistence and Core DataSelf paced8Udacity☆☆☆☆☆
How to Make an iOS AppSelf paced12Udacity☆☆☆☆☆
Android PerformanceSelf paced4Udacity☆☆☆☆☆
Android Development for BeginnersSelf paced4Udacity★★★★☆ (5 reviews)
Advanced Android App DevelopmentSelf paced6Udacity☆☆☆☆☆
Material Design for Android DevelopersSelf paced4Udacity☆☆☆☆☆
Android Ubiquitous ComputingSelf paced4Udacity☆☆☆☆☆
AMRx: Autonomous Mobile RobotsSelf pacedNAedX★★★☆☆ (3 reviews)
KIexploRx: Explore Statistics with RSelf pacedNAedX★★★★☆ (7 reviews)
Intro to DevOpsSelf paced3Udacity☆☆☆☆☆
Configuring Linux Web ServersSelf paced1Udacity☆☆☆☆☆
Learn Backbone.jsSelf paced2Udacity☆☆☆☆☆
How to create <anything> in AndroidSelf paced4Udacity☆☆☆☆☆
JavaScript Design PatternsSelf paced6Udacity★★★★★ (1 review)
ADVANCED(23)
Course NameStart DateLength (in weeks)ProviderRating
Genomic Data Science with Galaxy5th Oct, 20154Coursera★★☆☆☆ (5 reviews)
Command Line Tools for Genomic Data Science5th Oct, 20154Coursera☆☆☆☆☆
Algorithms for DNA Sequencing5th Oct, 20154Coursera★★★★★ (8 reviews)
Introduction to Natural Language Processing5th Oct, 201512Coursera☆☆☆☆☆
Finding Hidden Messages in DNA (Bioinformatics I)12th Oct, 20154Coursera★★★★☆ (8 reviews)
Hardware Security12th Oct, 20156Coursera★★★☆☆ (8 reviews)
Machine Learning Foundations: A Case Study Approach12th Oct, 20156Coursera☆☆☆☆☆
Deciphering Molecular Evolution (Bioinformatics IV)12th Oct, 20155Coursera☆☆☆☆☆
Comparing Genes, Proteins, and Genomes (Bioinformatics III)12th Oct, 20155Coursera☆☆☆☆☆
Artificial Intelligence for RoboticsSelf paced8Udacity★★★★★ (12 reviews)
Applied CryptographySelf paced8Udacity★★★★☆ (2 reviews)
Intro to Parallel ProgrammingSelf paced12Udacity★★★★☆ (2 reviews)
Interactive 3D GraphicsSelf paced8Udacity★★★★★ (3 reviews)
Functional Hardware VerificationSelf paced8Udacity★★★★★ (1 review)
Real-Time Analytics with Apache StormSelf paced2Udacity★★★★☆ (1 review)
Model Building and ValidationSelf paced8Udacity★★★☆☆ (3 reviews)
Advanced Operating SystemsSelf paced5Udacity★★★★★ (1 review)
High Performance Computer ArchitectureSelf pacedNAUdacity☆☆☆☆☆
Computability, Complexity & AlgorithmsSelf pacedNAUdacity☆☆☆☆☆
Knowledge-Based AI: Cognitive SystemsSelf paced7Udacity☆☆☆☆☆
Introduction to Recommender SystemsSelf pacedNACoursera★★★★☆ (10 reviews)
Machine LearningSelf paced16Udacity☆☆☆☆☆